| Title: | Naive Bayes Transmission Analysis |
|---|---|
| Description: | Estimates the relative transmission probabilities between cases in an infectious disease outbreak or cluster using naive Bayes. Included are various functions to use these probabilities to estimate transmission parameters such as the generation/serial interval and reproductive number as well as finding the contribution of covariates to the probabilities and visualizing results. The ideal use is for an infectious disease dataset with metadata on the majority of cases but more informative data such as contact tracing or pathogen whole genome sequencing on only a subset of cases. For a detailed description of the methods see Leavitt et al. (2020) <doi:10.1093/ije/dyaa031>. |
| Authors: | Sarah V Leavitt [aut, cre, cph] |
| Maintainer: | Sarah V Leavitt <[email protected]> |
| License: | MIT + file LICENSE |
| Version: | 1.1.4 |
| Built: | 2024-11-09 04:39:33 UTC |
| Source: | https://github.com/sarahleavitt/nbTransmission |
The function clusterInfectors uses either kernel density estimation or
hierarchical clustering to cluster the infectors for each infectee. This clustering
provides a way to separate out the few top possible infectors for each infectee
if there is such a cluster.
clusterInfectors( df, indIDVar, pVar, clustMethod = c("n", "kd", "hc_absolute", "hc_relative"), cutoff )clusterInfectors( df, indIDVar, pVar, clustMethod = c("n", "kd", "hc_absolute", "hc_relative"), cutoff )
df |
The name of the dateset with transmission probabilities (column |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
pVar |
The name (in quotes) of the column with transmission probabilities. |
clustMethod |
The method used to cluster the infectors;
one of |
cutoff |
The cutoff for clustering (see details). |
This function provides a way to find the most likely infectors for each infectee
using various clustering methods indicated by the clustmethod.
The methods can be one of c("n", "kd", "hc_constant", "hc_relative").
If clustMethod == "n" then this function simply assigns the top n possible
infectors in the top cluster where n is defined by the value of cutoff.
If clustMethod == "kd" then kernel density estimation is used to split the infectors.
The density for the probabilities for all infectors is estimated using a binwidth defined
by the value of cutoff. If the density is made up of at least two separate curves
(separated by a region where the density drops to 0) then the infectors with probabilities
greater than the lowest 0 region are assigned to the high probability cluster. If the density of the
probabilities does not drop to 0 then all infectors are assigned to the low probability cluster
(indicating no real clustering).
If clustMethod == "hc_absolute" or clustMethod == "hc_relative", then
hierarchical clustering with minimum distance is used to split the possible infectors
into two clusters. This method functionally splits the infectors by the largest gap
in their probabilities.
Then if clustMethod == "hc_absolute", those infectees
where the gap between the two clusters is less than cutoff have all of their
possible infectors reassigned to the low probability cluster (indicating no real clustering).
If clustMethod == "hc_relative", then all infectees where the gap between the two
clusters is less than cutoff times the second largest gap in probabilities
are reassigned to the low probability cluster (indicating no real clustering).
The original data frame (df) with a new column called cluster
which is a factor variable with value 1 if the infector is in the high probability cluster
or 2 if the infector is in the low probability cluster.
## Use the nbResults data frame included in the package which has the results ## of the nbProbabilities() function on a TB-like outbreak. ## Clustering using top n # High probability cluster includes infectors with highest 3 probabilities clust1 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "n", cutoff = 3) table(clust1$cluster) ## Clustering using hierarchical clustering # Cluster all infectees, do not force gap to be certain size clust2 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0) table(clust2$cluster) # Absolute difference: gap between top and bottom clusters is more than 0.05 clust3 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05) table(clust3$cluster) # Relative difference: gap between top and bottom clusters is more than double any other gap clust4 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_relative", cutoff = 2) table(clust4$cluster) ## Clustering using kernel density estimation # Using a small binwidth of 0.01 clust5 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "kd", cutoff = 0.01) table(clust5$cluster)## Use the nbResults data frame included in the package which has the results ## of the nbProbabilities() function on a TB-like outbreak. ## Clustering using top n # High probability cluster includes infectors with highest 3 probabilities clust1 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "n", cutoff = 3) table(clust1$cluster) ## Clustering using hierarchical clustering # Cluster all infectees, do not force gap to be certain size clust2 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0) table(clust2$cluster) # Absolute difference: gap between top and bottom clusters is more than 0.05 clust3 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05) table(clust3$cluster) # Relative difference: gap between top and bottom clusters is more than double any other gap clust4 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_relative", cutoff = 2) table(clust4$cluster) ## Clustering using kernel density estimation # Using a small binwidth of 0.01 clust5 <- clusterInfectors(nbResults, indIDVar = "individualID", pVar = "pScaled", clustMethod = "kd", cutoff = 0.01) table(clust5$cluster)
The function estimateR uses the relative transmission probabilities to estimate
the individual-level, time-level, and average effective reproductive numbers
for an outbreak.
estimateR( df, indIDVar, dateVar, pVar, timeFrame = c("days", "months", "weeks", "years"), rangeForAvg = NULL, bootSamples = 0, alpha = 0.05, progressBar = TRUE )estimateR( df, indIDVar, dateVar, pVar, timeFrame = c("days", "months", "weeks", "years"), rangeForAvg = NULL, bootSamples = 0, alpha = 0.05, progressBar = TRUE )
df |
The name of the dateset with transmission probabilities (column |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
dateVar |
The name (in quotes) of the columns with the dates that the individuals are
observed (data frame |
pVar |
The column name (in quotes) of the transmission probabilities. |
timeFrame |
The time frame used to calculate Rt
(one of |
rangeForAvg |
A vector with the start and ending time period to be used to calculate the average effective reproductive number. |
bootSamples |
The number of bootstrap samples; if 0, then no confidence intervals are calculated. |
alpha |
The alpha level for the confidence intervals. |
progressBar |
A logical indicating if a progress bar should be printed (default is TRUE). |
The effective reproductive number is the average number of cases an infectious case will produce in a population of both susceptible and non-susceptibe individuals. The rational behind this reproductive number estimation is Wallinga and Teunis (2004) where the individual-level reproductive number is estimated by summing the relative probability that the individual infected any other individual.
If equals the relative probability that case was infected by
case , then the individual-level reproductive number () is calculated by:
The time-level reproductive number is then estimated by averaging the individual-level reproductive numbers for all individuals observed in the time frame (can specify days, weeks, months, years).
Finally, the time-level reproductive numbers are averaged to
estimate the average effective reproductive number within rangeForAvg.
To get the best estimate of the average effective reproductive number, one should
only consider the stable portion of the outbreak (exclude the beginning and end).
If bootSamples > 0, bootstrap confidence intervals will be estimated for
both the time-level and average reproductive numbers using parametric bootstrapping.
A list with five elements:
RiDf - a data frame with the individual-level reproductive numbers. Column names:
<indIDVar> - the individual ID with name specified.
<dateVar> - the date the individual was observed with name specified.
Ri - the individual-level reproductive number.
nInfectees - the number of possible infectees for this individual.
RtDf - a data frame with the time-level reproductive numbers. Column names:
time - the time frame corresponding to the reproductive number estimate
(day for "days" and "weeks", month for "months", year for "years").
timeRank - the rank of the time frame.
Rt - the time-level reproductive number for this time frame.
ciLower - lower bound of confidence interval for Rt
(only if bootSamples > 0).
ciUpper - upper bound of confidence interval for Rt
(only if bootSamples > 0).
RtAvgDf - a data frame with the average effective reproductive. Column names:
RtAvg - the average time-level reproductive number between the range
specified in rangeForAvg.
ciLower - lower bound of confidence interval for Rt
(only if bootSamples > 0).
ciUpper - upper bound of confidence interval for Rt
(only if bootSamples > 0).
timeFrame - a vector with the timeFrame input
rangeForAvg - a vector with the rangeForAvg input
Wallinga J, Teunis P. Different epidemic curves for severe acute respiratory syndrome reveal similar impacts of control measures. American Journal of Epidemiology. 2004 Sep 15;160(6):509-16.
nbProbabilities estimateRi
estimateRt estimateRtAvg
## Use the nbResults data frame included in the package which has the results ## of the nbProbabilities() function on a TB-like outbreak. ## Getting initial estimates of the reproductive number # (without specifying rangeForAvg and without confidence intervals) rInitial <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months") ## Finding the stable portion of the outbreak for rangeForAvg using plot of Rt cut1 <- 25 cut2 <- 125 # Optional plot to determine the cutpoints above # ggplot(data = rInitial$RtDf, aes(x = timeRank, y = Rt)) + # geom_point() + # geom_line() + # geom_hline(data = rInitial$RtAvgDf, aes(yintercept = RtAvg), size = 0.7) + # geom_vline(aes(xintercept = cut1), linetype = 2, size = 0.7) + # geom_vline(aes(xintercept = cut2), linetype = 2, size = 0.7) ## Finding the final reproductive number estimates with confidence intervals # NOTE should run with bootSamples > 2. rFinal <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months", rangeForAvg = c(cut1, cut2), bootSamples = 2, alpha = 0.05) rFinal$RtAvgDf## Use the nbResults data frame included in the package which has the results ## of the nbProbabilities() function on a TB-like outbreak. ## Getting initial estimates of the reproductive number # (without specifying rangeForAvg and without confidence intervals) rInitial <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months") ## Finding the stable portion of the outbreak for rangeForAvg using plot of Rt cut1 <- 25 cut2 <- 125 # Optional plot to determine the cutpoints above # ggplot(data = rInitial$RtDf, aes(x = timeRank, y = Rt)) + # geom_point() + # geom_line() + # geom_hline(data = rInitial$RtAvgDf, aes(yintercept = RtAvg), size = 0.7) + # geom_vline(aes(xintercept = cut1), linetype = 2, size = 0.7) + # geom_vline(aes(xintercept = cut2), linetype = 2, size = 0.7) ## Finding the final reproductive number estimates with confidence intervals # NOTE should run with bootSamples > 2. rFinal <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months", rangeForAvg = c(cut1, cut2), bootSamples = 2, alpha = 0.05) rFinal$RtAvgDf
The function estimateRi uses relative transmission probabilities to estimate the
individual-level reproductive number.
estimateRi(df, indIDVar, dateVar, pVar)estimateRi(df, indIDVar, dateVar, pVar)
df |
The name of the dateset with transmission probabilities |
indIDVar |
The variable name (in quotes) of the individual ID varaibles
(data frame |
dateVar |
The variable name (in quotes) of the dates that the individuals
are observed (data frame |
pVar |
The variable name (in quotes) of the transmission probabilities. |
This function is meant to be called by estimateR
which estimates the individual-level, time-level, and average reproductive numbers,
but it can also be run directly.
A data frame with the individual-level reproductive numbers. Column names:
<indIDVar> - the individual ID with name specified.
<dateVar> - the date the individual was observed with name specified.
Ri - the individual-level reproductive number.
nInfectees - the number of possible infectees for this individual.
estimateR estimateRt estimateRtAvg
The function estimateRt estimates the time-level effective reproductive number
from individual-level reproductive numbers.
estimateRt(riData, dateVar, timeFrame = c("days", "weeks", "months", "years"))estimateRt(riData, dateVar, timeFrame = c("days", "weeks", "months", "years"))
riData |
The name of the dateset with individual-level reproductive numbers. |
dateVar |
The variable name (in quotes) of the dates that the individuals are observed
(data frame |
timeFrame |
The time frame used to calculate Rt
(one of |
This function is meant to be called by estimateR
which estimates the individual-level and time-level, and average reproductive numbers,
but it can also be run directly.
A data frame with the time-level reproductive numbers. Column names:
time - the time frame corresponding to the reproductive number estimate
(day for "days" and "weeks", month for "months", year for "years").
timeRank - the rank of the time frame.
Rt - the time-level reproductive number for this time frame.
estimateR estimateRi estimateRtAvg
Averages the time-level reproductive numbers within a certain range to estimate the overall reproductive number for an oubreak.
estimateRtAvg(rtData, rangeForAvg = NULL)estimateRtAvg(rtData, rangeForAvg = NULL)
rtData |
The name of the dateset with time-level reproductive numbers. |
rangeForAvg |
A vector with the start and ending time period to be used to calculate the average effective reproductive number. |
This function is meant to be called by estimateR
which estimates the individual-level and time-level, and average reproductive numbers,
but it can also be run directly.
A data frame with the average effective reproductive. Column names:
RtAvg - the average time-level reproductive number between the range
specified in rangeForAvg.
estimateR estimateRi estimateRt
The function estimateSI uses the relative transmission probabilities to estimate
the generation/serial interval distribution assuming a gamma distribution.
It uses the PEM algorithm developed by Hens et al. 2012 extending their method to include
restricting analysis to the top cluster of possible infectors.
estimateSI( df, indIDVar, timeDiffVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoffs = NULL, initialPars, shift = 0, epsilon = 1e-05, bootSamples = 0, alpha = 0.05, progressBar = TRUE )estimateSI( df, indIDVar, timeDiffVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoffs = NULL, initialPars, shift = 0, epsilon = 1e-05, bootSamples = 0, alpha = 0.05, progressBar = TRUE )
df |
The name of the dateset with transmission probabilities (column |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
timeDiffVar |
The name (in quotes) of the column with the difference in time between infection (generation interval) or symptom onset (serial interval) for the pair of cases. The units of this variable (hours, days, years) defines the units of the resulting distribution. |
pVar |
The column name (in quotes) of the transmission probabilities. |
clustMethod |
The method used to cluster the infectors; one of
|
cutoffs |
A vector of cutoffs for clustering (see |
initialPars |
A vector of length two with the shape and scale to initialize the gamma distribution parameters. |
shift |
A value in the same units as |
epsilon |
The difference between successive estimates of the shape and scale parameters that indicates convergence. |
bootSamples |
The number of bootstrap samples; if 0, then no confidence intervals are calculated. |
alpha |
The alpha level for the confidence intervals. |
progressBar |
A logical indicating if a progress bar should be printed (default is TRUE). |
The PEM algorithm uses the prior probability that each pair is connected by direct
transmission to estimate the generation/serial interval using estimation maximization.
This code will provide an estimate of the generation interval if timeDiffVar represents the
difference in infection dates and the serial interval if it represents the difference in symptom onset dates.
The current generation/serial interval distribution parameters are used to update the probabilities
which are then used to update the generation/serial interval distribution parameters. The process
continues until the parameters converge (indicated by a change of less than epsilon)
between iterations. Note: time difference between pairs should not be used to
estimate the probabilities
This function acts as a wrapper around performPEM which integrates
estimation of the generation/serial interval distribution with clustering the infectors and calculates
derived parameters (mean, median, sd) of the distribution. Generally, this function
should be called instead of performPEM directly.
All pairs of cases can be used in the estimation process by setting
clustMethod = "none". However, if the probabilities are from a algorithm such as
nbProbabilities, then it is recommeneded to use a clustering method
and only include the top cluster of infectors for infectees which have such a cluster.
This can be specified by using the clustMethod and cutoff arguments which
are passed into clusterInfectors. See the details of this function for
a description of the different clustering methods.
The method can be performed with any generation/serial interval distribution,
but this version of this function assumes that the generation/serial interval has a gamma distribution.
The function does allow for a shifted gamma distribution. The shift argument
defines how much the gamma distribution should be shifted. Any observed generation/serial intervals
that are less than this shift will have probability 0. This parameter should be used if
there is a clinical lower bound for the possible generation/serial interval. If this argument
is not specified then an unmodified gamma function is used. The units of the
estimated gamma distribution will be defined by the units of the provided
<timeDiffVar> column. The value of the shift should be in the same units.
The algorithm requires initial parameters which should be specified as a vector:
c(<shape>, <scale>). These parameters should result in a gamma distribution
that is on the desired scale, set by the <timeDiffVar> column.
If bootSamples > 0, bootstrap confidence intervals will be estimated for
both the shape and scale parameters as well as the mean, median, and mode of the
distribution using cluster bootstrapping.
A data frame with one row and the following columns:
nIndividuals - the number of infectees who have intervals included in the estimate.
pCluster - the proportion of cases who have intervals included in the estimate.
nInfectors - the average number of infectors in the top cluster.
shape - the shape of the estimated gamma distribution for the interval
scale - the scale of the estimated gamma distribution for the interval
meanSI - the mean of the estimated gamma distribution for the interval
(shape * scale + shift)
medianSI - the median of the estimated gamma distribution for the interval
(qgamma(0.5, shape, scale) + shift))
sdSI - the standard deviation of the estimated gamma distribution for
the interval (shape * scale ^ 2)
If bootSamples > 0, then the data frame also includes the following columns:
shapeCILB and shapeCIUB - lower bound and upper bounds
of the bootstrap confidence interval for the shape parameter
scaleCILB and scaleCIUB - lower bound and upper bounds
of the bootstrap confidence interval for the scale parameter
meanCILB and meanCIUB - lower bound and upper bounds
of the bootstrap confidence interval for the mean of the interval distribution
medianCILB and medianCIUB - lower bound and upper bounds
of the bootstrap confidence interval for the median of the interval distribution
sdCILB and sdCIUB - lower bound and upper bounds
of the bootstrap confidence interval for the sd of the interval distribution
Hens N, Calatayud L, Kurkela S, Tamme T, Wallinga J. Robust reconstruction and analysis of outbreak data: influenza A (H1N1) v transmission in a school-based population. American Journal of Epidemiology. 2012 Jul 12;176(3):196-203.
nbProbabilities clusterInfectors
performPEM
## First, run the algorithm without including time as a covariate. orderedPair <- pairData[pairData$infectionDiffY > 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm # NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResultsNoT <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE) ## Estimating the serial interval # Using hierarchical clustering with a 0.05 absolute difference cutoff estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2)) # Using all pairs estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "none", initialPars = c(2, 2)) # # Using a shifted gamma distribution: # # not allowing serial intervals of less than 3 months (0.25 years) estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2), shift = 0.25) # # Using multiple cutoffs estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = c(0.025, 0.05), initialPars = c(2, 2)) ## Adding confidence intervals # NOTE should run with bootSamples > 2. estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2), shift = 0.25, bootSamples = 2)## First, run the algorithm without including time as a covariate. orderedPair <- pairData[pairData$infectionDiffY > 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm # NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResultsNoT <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE) ## Estimating the serial interval # Using hierarchical clustering with a 0.05 absolute difference cutoff estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2)) # Using all pairs estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "none", initialPars = c(2, 2)) # # Using a shifted gamma distribution: # # not allowing serial intervals of less than 3 months (0.25 years) estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2), shift = 0.25) # # Using multiple cutoffs estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = c(0.025, 0.05), initialPars = c(2, 2)) ## Adding confidence intervals # NOTE should run with bootSamples > 2. estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2), shift = 0.25, bootSamples = 2)
A dataset of an outbreak of 100 individuals starting from one case. It was simulated with using the package TransPhylo with parameters resembling TB:
average reproductive number = 1.2
generation interval = gamma(1.2, 2) years
outbreak duration = 14 years
mutation rate 0.5 snps/genome/year
indDataindData
A data frame with 100 rows and 8 variables:
An individual-level id for each case.
The individualID of the true infector.
The date and time of infection.
The date and time of sampling.
Covariate with 2 values: a, b (e.g. sex).
Covariate with 4 values: a, b, c, d (e.g. nationality).
Covariate with 2 values: a, b (e.g. homelessness).
Covariate with 10 values: a-j (e.g. county of residence).
Didelot X, Fraser C, Gardy J, Colijn C. Genomic Infectious Disease Epidemiology in Partially Sampled and Ongoing Outbreaks. Mol Biol Evol. 2017;34(4):997-1007.
The function indToPair takes a dataset of observations (such as individuals in an infectious
disease outbreak) and transforms it into a dataset of pairs.
indToPair( indData, indIDVar, separator = "_", dateVar = NULL, units = c("mins", "hours", "days", "weeks"), ordered = FALSE )indToPair( indData, indIDVar, separator = "_", dateVar = NULL, units = c("mins", "hours", "days", "weeks"), ordered = FALSE )
indData |
An individual-level dataframe. |
indIDVar |
The name (in quotes) of the column with the individual ID. |
separator |
The character to be used to separate the individual IDs when creating the pairID. |
dateVar |
The name (in quotes) of the column with the dates that the individuals are observed
(optional unless |
units |
The units for the time difference, only necessary if |
ordered |
A logical indicating if a set of ordered pairs should be returned
( |
The function requires an id column: indIDVar to identify the individual observations.
The resulting pair-level dataframe will have a pairID column which combines the individual IDs
for that pair.
The function can either output all possible pairs (ordered = FALSE) or only ordered pairs
(ordered = TRUE) where the ordered is determined by a date variable (dateVar).
If orded = TRUE, then dateVar must be provided and if ordered = FALSE,
it is optional. In both cases, if dateVar is provided, the output will include the time
difference between the individuals in the pair in the units specified ("mins", "hours", "days", "weeks").
A dataframe of either all possible pairs of individuals (ordered = FALSE) or ordered
pairs of individuals (ordered = TRUE). The dataframe will have all of the original variables
with suffixes ".1" and ".2" corresponding to the original values of
<indIDVar>.1 and <indIDVar>.2.
Added to the dataframe will be a column called pairID which is <indIDVar>.1
and <indIDVar>.2 separated by separator.
If dateVar is provided the dataframe will also include variables <dateVar>.Diff giving
the difference of time of dateVar for <indIDVar>.1 and <indIDVar>.2
in the units specified
## Create a dataset of all pairs with no date variable pairU <- indToPair(indData = indData, indIDVar = "individualID") ## Create a dataset of all pairs with a date variable pairUD <- indToPair(indData = indData, indIDVar = "individualID", dateVar = "infectionDate", units = "days") ## Create a dataset of ordered pairs pairO <- indToPair(indData = indData, indIDVar = "individualID", dateVar = "infectionDate", units = "days", ordered = TRUE)## Create a dataset of all pairs with no date variable pairU <- indToPair(indData = indData, indIDVar = "individualID") ## Create a dataset of all pairs with a date variable pairUD <- indToPair(indData = indData, indIDVar = "individualID", dateVar = "infectionDate", units = "days") ## Create a dataset of ordered pairs pairO <- indToPair(indData = indData, indIDVar = "individualID", dateVar = "infectionDate", units = "days", ordered = TRUE)
The function nbHeatmap plots a heatmap of the transmission probabilities.
The rows are the possible infectors and the columns are the possible infectees both
ordered by <dateVar>. The darker the square the higher the probability that
the pair represented by that square is a transmission link. If a cluster method is specified
using clustMethod and cutoff, then stars will be drawn in the squares of the
infectors in the top cluster.
nbHeatmap( df, indIDVar, dateVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoff = NA, blackAndWhite = FALSE, probBreaks = c(-0.01, 0.001, 0.005, 0.01, 0.05, 0.1, 0.25, 0.5, 0.75, 1) )nbHeatmap( df, indIDVar, dateVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoff = NA, blackAndWhite = FALSE, probBreaks = c(-0.01, 0.001, 0.005, 0.01, 0.05, 0.1, 0.25, 0.5, 0.75, 1) )
df |
The name of the dateset with transmission probabilities (column |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
dateVar |
The name (in quotes) of the columns with the dates that the individuals are
observed (data frame |
pVar |
The name (in quotes) of the column with transmission probabilities. |
clustMethod |
The method used to cluster the infectors; one of
|
cutoff |
The cutoff for clustering (see |
blackAndWhite |
A logical. If |
probBreaks |
A numeric vector containing between 3 and 10 elements specifying the boundaries used to classify the probabilities and color the squares. The first element should be less than 0 and the last should be 1. |
Users have the option of specifying how the probabilities should be grouped into different
color shades through the argument probBreaks. The probabilities are split into groups by
using probBreaks as the breaks argument in cut with the default options.
The length of the vector should be between 3 and 10 and the first element should be less than 0 and
the last 1 so that all probabilities are guarenteed to be classified.
The colors are defined with the code brewer.pal(length(probBreaks) - 1, "Blues")
(where "Blues" is replaced by "Greys" if blackAndWhite is set to TRUE).
NOTE: This plot will take long to run and may not look good with larger outbreaks (>200 individuals)
nbProbabilities clusterInfectors
## Heatmap with no clustering in color with the default probability breaks par(mar = c(0, 0, 1, 0)) nbHeatmap(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "none") dev.off() ## Adding stars for the top cluster, in black and white, changing the probability breaks par(mar = c(0, 0, 1, 0)) nbHeatmap(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, blackAndWhite = TRUE, probBreaks = c(-0.01, 0.01, 0.1, 0.25, 0.5, 1)) dev.off()## Heatmap with no clustering in color with the default probability breaks par(mar = c(0, 0, 1, 0)) nbHeatmap(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "none") dev.off() ## Adding stars for the top cluster, in black and white, changing the probability breaks par(mar = c(0, 0, 1, 0)) nbHeatmap(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, blackAndWhite = TRUE, probBreaks = c(-0.01, 0.01, 0.1, 0.25, 0.5, 1)) dev.off()
The function nNetwork plots a network of the transmission probabilities.
The nodes are the individuals and the edges represent possible transmission pairs.
The darker the edge, the higher the probability that the pair is a transmission link.
If a cluster method is specified using clustMethod and cutoff, only edges
that are in the high probability cluster of infectors will be drawn.
nbNetwork( df, indIDVar, dateVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoff = NA, blackAndWhite = FALSE, probBreaks = c(-0.01, 0.001, 0.005, 0.01, 0.05, 0.1, 0.25, 0.5, 0.75, 1) )nbNetwork( df, indIDVar, dateVar, pVar, clustMethod = c("none", "n", "kd", "hc_absolute", "hc_relative"), cutoff = NA, blackAndWhite = FALSE, probBreaks = c(-0.01, 0.001, 0.005, 0.01, 0.05, 0.1, 0.25, 0.5, 0.75, 1) )
df |
The name of the dateset with transmission probabilities (column |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
dateVar |
The name (in quotes) of the columns with the dates that the individuals are
observed (data frame |
pVar |
The name (in quotes) of the column with transmission probabilities. |
clustMethod |
The method used to cluster the infectors; one of
|
cutoff |
The cutoff for clustering (see |
blackAndWhite |
A logical. If |
probBreaks |
A numeric vector containing between 3 and 10 elements specifying the boundaries used to classify the probabilities and color the edges. The first element should be less than 0 and the last should be 1. |
Users have the option of specifying how the probabilities should be grouped into different
color shades through the argument probBreaks. The probabilities are split into groups by
using probBreaks as the breaks argument in cut with the default options.
The length of the vector should be between 3 and 10 and the first element should be less than 0 and
the last 1 so that all probabilities are guarenteed to be classified.
The colors are defined with the code brewer.pal(length(probBreaks) - 1, "Blues")
(where "Blues" is replaced by "Greys" if blackAndWhite is set to TRUE).
nbProbabilities clusterInfectors
## Network of all pairs in color with the default probability breaks par(mar = c(0, 0, 0.2, 0)) nbNetwork(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "none") dev.off() ## Network of just the top cluster of infectors, black and white, changing the probability breaks par(mar = c(0, 0, 0.2, 0)) nbNetwork(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, blackAndWhite = TRUE, probBreaks = c(-0.01, 0.01, 0.1, 0.25, 0.5, 1)) dev.off()## Network of all pairs in color with the default probability breaks par(mar = c(0, 0, 0.2, 0)) nbNetwork(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "none") dev.off() ## Network of just the top cluster of infectors, black and white, changing the probability breaks par(mar = c(0, 0, 0.2, 0)) nbNetwork(nbResults, indIDVar = "individualID", dateVar = "infectionDate", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, blackAndWhite = TRUE, probBreaks = c(-0.01, 0.01, 0.1, 0.25, 0.5, 1)) dev.off()
The function nbProbabilities uses naive Bayes and an interative estimation
procedure to estimate relative transmission probabilities
nbProbabilities( orderedPair, indIDVar, pairIDVar, goldStdVar, covariates, label = "", l = 1, n = 10, m = 1, nReps = 10, progressBar = TRUE )nbProbabilities( orderedPair, indIDVar, pairIDVar, goldStdVar, covariates, label = "", l = 1, n = 10, m = 1, nReps = 10, progressBar = TRUE )
orderedPair |
The name of the ordered pair-level dataset with the covariates. |
indIDVar |
The name (in quotes) of the column with the individual ID.
(data frame |
pairIDVar |
The name (in quotes) of the column with the unique pair ID variable. |
goldStdVar |
The name (in quotes) of the column with a logical vector defining training links/non-links |
covariates |
A character vector containing the covariate column names (in quotes). All covariates need to be categorical factor variables. |
label |
An optional label string for the run. |
l |
Laplace smoothing parameter that is added to each cell. |
n |
The number of folds for nxm cross validation (should be at least 10). |
m |
The number of times to create n folds in nxm cross validation. |
nReps |
The number of times to randomly select the "true" infector (should be at least 10). |
progressBar |
A logical indicating if a progress bar should be printed (default is TRUE). |
This algorithm takes a dataset of ordered possible infector-infectee pairs in an infectious disease outbreak or cluster and estimates the relative probability the cases are linked by direct transmission using a classification technique called naive Bayes (NB). NB is a simple machine learning algorithm that uses Bayes rule to estimate the probability of an outcome in a prediction dataset given a set of covariates from the observed frequencies in a training dataset.
The input dataset - orderedPair - should represent ordered pairs of cases
(where the potential infector was observed before the infectee) and have
a unique identifier for each pair (pairIDVar) as well as the individual ids that are
included in the pair (<indIDVar>.1 and <indIDVar>.2). If cases are concurrent
(meaning the order cannot determined) both orders can be included.
A subset of pairs should also have pathogen WGS, contact investigation, or some other
'gold standard' defined by goldStdVar which should be a logical vector with
TRUE indicating links, FALSE nonlinks, and NA if
the pair cannot be used to train (does not have the information or is indeterminate).
These pairs will be used to a training dataset of probable links and non/links.
The covariates can be any categorical variables and could represent
spatial, clinical, demographic, and temporal characteristics of the case pair.
Because the outcomes in the training set represent probable and not certain
transmission events and a given case could have mulitple probable infectors,
the algorithm uses an iterative estimation procedure. This procedure randomly chooses one
link of all of the possible links to include in the training dataset nReps
times, and then uses mxn cross prediction to give all pairs a turn
in the prediction dataset.
The output of this function is a list of two dataframes: one with the estimates of the
transmission probabilities (probabilities) and the other with the contribution of
the covariates to the probabilities in the form of odds ratios (estimates). The
95
for multiple imputation, to pool the error across all iterations.
List containing two data frames:
probabilities - a data frame of transmission probabilities. Column names:
label - the optional label of the run.
<pairIDVar> - the pair ID with the name specified.
pAvg - the mean transmission probability for the pair over all iterations.
pSD - the standard deviation of the transmission probability for the pair
over all iterations.
pScaled - the mean relative transmission probability for the pair over.
all iterations: pAvg scaled so that the probabilities for all infectors per infectee add to 1.
pRank - the rank of the probability of the the pair out of all pairs for that
infectee (in case of ties all values have the minimum rank of the group).
nEstimates - the number of probability estimates that contributed to pAvg. This
represents the number of prediction datasets this pair was included in over the nxm
cross prediction repeated nReps times.
estimates - a data frame with the contribution of covariates. Column names:
label - the optional label of the run
level - the covariate name and level
nIter - the number of iterations included in the estimates: n*m*nReps
logorMean - the mean value of the log odds ratio across iterations
logorSE - the standard error of the log odds ratio across iterations
logorCILB - the lower bound of the 95
across iterations
logorCIUB - the upper bound of the 95
across iterations
Barnard J. and Rubin D. Small-Sample Degrees of Freedom with Multiple Imputation Biometrika. 1999 Dec;86(4):948-55.
## Use the pairData dataset which represents a TB-like outbreak # First create a dataset of ordered pairs orderedPair <- pairData[pairData$infectionDiffY >= 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm #NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4", "timeCat"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResults <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE)## Use the pairData dataset which represents a TB-like outbreak # First create a dataset of ordered pairs orderedPair <- pairData[pairData$infectionDiffY >= 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm #NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4", "timeCat"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResults <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE)
nbProbabilities
A ordered dataset created from pairData of the outbreak of 100 individuals
including the relative transmission probabilities for each pair estimated using the function
nbProbabilities. The code to recreate this dataset from pairData
is shown below.
nbResultsnbResults
A data frame with 9900 rows and 24 variables:
A pair-level ID variable (the individual IDs separated by an '_').
The label for the run, here "SNPs".
The mean transmission probability for the pair over all runs.
The standard deviation of the transmission probability for the pair over all runs.
The mean relative transmission probability for the pair over all runs: pAvg scaled so that the probabilities for all infectors per infectee add to 1.
The rank of the probability of the the pair out of all pairs for that infectee (in case of ties all values have the minimum rank of the group).
The number of probability estimates that contributed to pAvg. This represents the number of prediction datasets this pair was included in over the 10x1 cross prediction repeated 50 times.
The ID of the potential "infector".
The ID of the potential "infectee".
Did individual.1 truly infect individual.2?
The number of SNPs between the individuals.
The date and time of infection of individualID.1.
The date and time of infection of individualID.2.
The date and time of sampling of individualID.1.
The date and time of sampling of individualID.2.
The number of days between sampleDate.1 and sampleDate.2.
The number of days between infectionDate.1 and infectionDate.2.
The number of years between infectionDate.1 and infectionDate.2.
A categorical representation of infectionDiff: <1y, 1-2y, 2-3y, 3-4y, 4-5y, >5y.
Pair-level covariate derived from X1: 1 if match, 0 if not match.
Pair-level covariate derived from X2: 1 if match, 0 if not match.
Pair-level covariate derived from X3: 1 if a-a, 2 if b-b, 3 if a-b, 4 if b-a.
Pair-level covariate derived from X4: 1 if match, 2 if adjacent, 2 otherwise.
Logical value indicating if a pair is a probable link. TRUE if the pair has fewer than 3 SNPs, FALSE if the pair has more than 12 SNPs, NA otherwise
# ## NOT RUN ## # ## This is the code used to create this dataset ## # orderedPair <- pairData[pairData$infectionDiff > 0, ] # orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, # ifelse(orderedPair$snpDist > 12, FALSE, NA)) # set.seed(0) # covariates = c("Z1", "Z2", "Z3", "Z4", "timeCat") # resGen <- nbProbabilities(orderedPair = orderedPair, # indIDVar = "individualID", # pairIDVar = "pairID", # goldStdVar = "snpClose", # covariates = covariates, # label = "SNPs", l = 1, # n = 10, m = 1, nReps = 50) # nbResults <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE)# ## NOT RUN ## # ## This is the code used to create this dataset ## # orderedPair <- pairData[pairData$infectionDiff > 0, ] # orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, # ifelse(orderedPair$snpDist > 12, FALSE, NA)) # set.seed(0) # covariates = c("Z1", "Z2", "Z3", "Z4", "timeCat") # resGen <- nbProbabilities(orderedPair = orderedPair, # indIDVar = "individualID", # pairIDVar = "pairID", # goldStdVar = "snpClose", # covariates = covariates, # label = "SNPs", l = 1, # n = 10, m = 1, nReps = 50) # nbResults <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE)
A dataset of all pairs (unordered) of the outbreak of 100 individuals
described in indData with SNP distance between each pair. Genomes were
simulated using the package phangorn from the phylogentic tree created
during the outbreak simulation.
pairDatapairData
A data frame with 9900 rows and 17 variables:
A pair-level ID variable (the individual IDs separated by an '_').
The ID of the potential "infector".
The ID of the potential "infectee".
Did individual.1 infect individual.2.
What is the number of SNPs between the individuals.
The date and time of infection of individualID.1.
The date and time of infection of individualID.2.
The date and time of sampling of individualID.1.
The date and time of sampling of individualID.2.
The number of days between sampleDate.1 and sampleDate.2.
The number of days between infectionDate.1 and infectionDate.2.
The number of years between infectionDate.1 and infectionDate.2.
A categorical representation of infectionDiff: <1y, 1-2y, 2-3y, 3-4y, 4-5y, >5y.
Pair-level covariate derived from X1: 1 if match, 0 if not match.
Pair-level covariate derived from X2: 1 if match, 0 if not match.
Pair-level covariate derived from X3: 1 if a-a, 2 if b-b, 3 if a-b, 4 if b-a.
Pair-level covariate derived from X4: 1 if match, 2 if adjacent, 2 otherwise.
Schliep KP. phangorn: Phylogenetic analysis in R. Bioinformatics. 2011;27(4):592-3.
The function performNB Calculates the posterior probabilities of a dichotomous class
variable given a set of covariates using Bayes rule.
performNB(training, prediction, obsIDVar, goldStdVar, covariates, l = 1)performNB(training, prediction, obsIDVar, goldStdVar, covariates, l = 1)
training |
The training dataset name. |
prediction |
The prediction dataset name. |
obsIDVar |
The variable name (in quotes) of the observation ID variable. |
goldStdVar |
The variable name (in quotes) of the outcome in the training dataset
(needs to be a logical variable with value |
covariates |
A character vector containing the covariate variable names. All covariates need to be categorical factor variables. |
l |
Laplace smoothing parameter that is added to each cell (a value of 0 indicates no smoothing). |
The main purpose of this function is to be used by nbProbabilities to
estimate the relative transmission probability between individuals in an infectious
disease outbreak. However, it can be used more generally to estimate the probability
of any dichotomous outcome given a set of categorical covariates.
The function needs a training dataset with the outcome variable (goldStdVar)
which is TRUE for those who have the value of interest and FALSE
for those who do not. The probability of having the outcome
(<goldStdVar> = TRUE) is predicted in the prediction dataset.
List containing two dataframes:
probabilities - a dataframe combining training and prediction
with predictied probabilities for the prediction dataframe. Column names:
<obsIDVar> - the observation ID with the name specified
p - the probability that <goldStdVar> = TRUE for observations in the
prediction dataset.
estimates - a dataframe with the effect estimates derived from the training dataset.
Column names:
level - the covariate name and level
est - the log odds ratio for this covariate and level
se - the standard error of the log odds ratio
## Use iris dataset and predict if a flower is of the specices "virginica". data(iris) irisNew <- iris ## Creating an id variable irisNew$id <- seq(1:nrow(irisNew)) ## Creating logical variable indicating if the flower is of the species virginica irisNew$spVirginica <- irisNew$Species == "virginica" ## Creating categorical/factor versions of the covariates irisNew$Sepal.Length.Cat <- factor(cut(irisNew$Sepal.Length, c(0, 5, 6, 7, Inf)), labels = c("<=5.0", "5.1-6.0", "6.1-7.0", "7.1+")) irisNew$Sepal.Width.Cat <- factor(cut(irisNew$Sepal.Width, c(0, 2.5, 3, 3.5, Inf)), labels = c("<=2.5", "2.6-3.0", "3.1-3.5", "3.6+")) irisNew$Petal.Length.Cat <- factor(cut(irisNew$Petal.Length, c(0, 2, 4, 6, Inf)), labels = c("<=2.0", "2.1-4.0", "4.1-6.0", "6.0+")) irisNew$Petal.Width.Cat <- factor(cut(irisNew$Petal.Width, c(0, 1, 2, Inf)), labels = c("<=1.0", "1.1-2.0", "2.1+")) ## Using NB to predict if the species is virginica ## (training and predicting on same dataset) pred <- performNB(irisNew, irisNew, obsIDVar = "id", goldStdVar = "spVirginica", covariates = c("Sepal.Length.Cat", "Sepal.Width.Cat", "Petal.Length.Cat", "Petal.Width.Cat"), l = 1) irisResults <- merge(irisNew, pred$probabilities, by = "id") tapply(irisResults$p, irisResults$Species, summary)## Use iris dataset and predict if a flower is of the specices "virginica". data(iris) irisNew <- iris ## Creating an id variable irisNew$id <- seq(1:nrow(irisNew)) ## Creating logical variable indicating if the flower is of the species virginica irisNew$spVirginica <- irisNew$Species == "virginica" ## Creating categorical/factor versions of the covariates irisNew$Sepal.Length.Cat <- factor(cut(irisNew$Sepal.Length, c(0, 5, 6, 7, Inf)), labels = c("<=5.0", "5.1-6.0", "6.1-7.0", "7.1+")) irisNew$Sepal.Width.Cat <- factor(cut(irisNew$Sepal.Width, c(0, 2.5, 3, 3.5, Inf)), labels = c("<=2.5", "2.6-3.0", "3.1-3.5", "3.6+")) irisNew$Petal.Length.Cat <- factor(cut(irisNew$Petal.Length, c(0, 2, 4, 6, Inf)), labels = c("<=2.0", "2.1-4.0", "4.1-6.0", "6.0+")) irisNew$Petal.Width.Cat <- factor(cut(irisNew$Petal.Width, c(0, 1, 2, Inf)), labels = c("<=1.0", "1.1-2.0", "2.1+")) ## Using NB to predict if the species is virginica ## (training and predicting on same dataset) pred <- performNB(irisNew, irisNew, obsIDVar = "id", goldStdVar = "spVirginica", covariates = c("Sepal.Length.Cat", "Sepal.Width.Cat", "Petal.Length.Cat", "Petal.Width.Cat"), l = 1) irisResults <- merge(irisNew, pred$probabilities, by = "id") tapply(irisResults$p, irisResults$Species, summary)
The function performPEM uses relative transmission probabilities to estimate
the generation/serial interval distribution
performPEM( df, indIDVar, timeDiffVar, pVar, initialPars, shift = 0, epsilon = 1e-05, plot = FALSE )performPEM( df, indIDVar, timeDiffVar, pVar, initialPars, shift = 0, epsilon = 1e-05, plot = FALSE )
df |
The name of the dateset with transmission probabilities. |
indIDVar |
The name (in quotes) of the individual ID columns
(data frame |
timeDiffVar |
The name (in quotes) of the column with the difference in time between infection (generation interval) or symptom onset (serial interval) for the pair of cases. The units of this variable (hours, days, years) defines the units of the resulting distribution. |
pVar |
The column name (in quotes) of the transmission probabilities. |
initialPars |
A vector of length two with the shape and scale to initialize the gamma distribution parameters. |
shift |
A value in the same units as |
epsilon |
The difference between successive estimates of the shape and scale parameters that indicates convergence. |
plot |
A logical indicating if a plot should be printed showing the parameter estimates at each iteration. |
This function is meant to be called by estimateSI
which estimates the generation/serial interval distribution as well as clustering the
probabilities, but can be called directly. The main reason to call performPEM
directly is for the plot argument. Setting this argument to TRUE
will produce a plot of the shape and scale parameters at each iteration.
For more details on the PEM algorithm see estimateSI.
A data frame with one row and the following columns:
nIndividuals - the number of infectees who have intervals included
in the SI estimate.
shape - the shape of the estimated gamma distribution for the interval.
scale - the scale of the estimated gamma distribution for the interval.
meanSI - the mean of the estimated gamma distribution for the interval
(shape * scale + shift).
medianSI - the median of the estimated gamma distribution for the interval
(qgamma(0.5, shape, scale) + shift)).
sdSI - the standard deviation of the estimated gamma distribution for
the interval (shape * scale ^ 2)
Hens N, Calatayud L, Kurkela S, Tamme T, Wallinga J. Robust reconstruction and analysis of outbreak data: influenza A (H1N1) v transmission in a school-based population. American Journal of Epidemiology. 2012 Jul 12;176(3):196-203.
nbProbabilities clusterInfectors
performPEM
## First, run the algorithm without including time as a covariate. orderedPair <- pairData[pairData$infectionDiffY > 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm #NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResultsNoT <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE) ## Estimating the serial interval # Using all pairs and plotting the parameters performPEM(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", initialPars = c(2, 2), shift = 0, plot = TRUE) # Clustering the probabilities first allClust <- clusterInfectors(nbResultsNoT, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05) performPEM(allClust[allClust$cluster == 1, ], indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", initialPars = c(2, 2), shift = 0, plot = TRUE) # The above is equivalent to the following code using the function estimateSI() # though the plot will not be printed and more details will be added estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2))## First, run the algorithm without including time as a covariate. orderedPair <- pairData[pairData$infectionDiffY > 0, ] ## Create a variable called snpClose that will define probable links # (<3 SNPs) and nonlinks (>12 SNPs) all pairs with between 2-12 SNPs # will not be used to train. orderedPair$snpClose <- ifelse(orderedPair$snpDist < 3, TRUE, ifelse(orderedPair$snpDist > 12, FALSE, NA)) table(orderedPair$snpClose) ## Running the algorithm #NOTE should run with nReps > 1. resGen <- nbProbabilities(orderedPair = orderedPair, indIDVar = "individualID", pairIDVar = "pairID", goldStdVar = "snpClose", covariates = c("Z1", "Z2", "Z3", "Z4"), label = "SNPs", l = 1, n = 10, m = 1, nReps = 1) ## Merging the probabilities back with the pair-level data nbResultsNoT <- merge(resGen[[1]], orderedPair, by = "pairID", all = TRUE) ## Estimating the serial interval # Using all pairs and plotting the parameters performPEM(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", initialPars = c(2, 2), shift = 0, plot = TRUE) # Clustering the probabilities first allClust <- clusterInfectors(nbResultsNoT, indIDVar = "individualID", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05) performPEM(allClust[allClust$cluster == 1, ], indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", initialPars = c(2, 2), shift = 0, plot = TRUE) # The above is equivalent to the following code using the function estimateSI() # though the plot will not be printed and more details will be added estimateSI(nbResultsNoT, indIDVar = "individualID", timeDiffVar = "infectionDiffY", pVar = "pScaled", clustMethod = "hc_absolute", cutoff = 0.05, initialPars = c(2, 2))
The function plotRt creates a plot of the effective reproductive number (Rt) over
the course of the outbreak. Using various options, the plot can include the overall average
Rt value for the outbreak and the confidence intervals.
plotRt( rData, includeRtAvg = FALSE, includeRtCI = FALSE, includeRtAvgCI = FALSE )plotRt( rData, includeRtAvg = FALSE, includeRtCI = FALSE, includeRtAvgCI = FALSE )
rData |
A list that is the output of |
includeRtAvg |
A logical. If TRUE, a horizontal line will be drawn for the average
Rt value over |
includeRtCI |
A logical. If TRUE, error bars will be added to the Rt values representing the bootstrap confidence intervals. |
includeRtAvgCI |
A logical. If TRUE, horizontal lines will be drawn around the Rt average line representing the bootstrap confidence interval. |
The main input rData should be the output of estimateRt with the
time-level reproductive numbers, overall average, range used to calculate that average,
and time frame.
The options includeRtCI and includeRtAvgCI add confidence interval bounds
to the plot. If set to true, rData should be from a call of estimateRt
with bootSamples > 0 so that confidence intervals are available.
If includeRtAvgCI is set to TRUE, a line for the point estimate of the average
Rt value will be drawn even if includeRtAvg is set to FALSE.
## Use the nbResults data frame included in the package which has the results # of the nbProbabilities() function on a TB-like outbreak. ## Getting initial estimates of the reproductive number # (without specifying nbResults and without confidence intervals) rInitial <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months") ## Finding the stable portion of the outbreak for rangeForAvg using the plot plotRt(rInitial) cut1 <- 25 cut2 <- 125 ## Finding the final reproductive number estimates with confidence intervals # NOTE should run with bootSamples > 10. rFinal <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months", rangeForAvg = c(cut1, cut2), bootSamples = 10, alpha = 0.05) ## Ploting the final result plotRt(rFinal, includeRtAvg = TRUE, includeRtCI = TRUE, includeRtAvgCI = TRUE)## Use the nbResults data frame included in the package which has the results # of the nbProbabilities() function on a TB-like outbreak. ## Getting initial estimates of the reproductive number # (without specifying nbResults and without confidence intervals) rInitial <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months") ## Finding the stable portion of the outbreak for rangeForAvg using the plot plotRt(rInitial) cut1 <- 25 cut2 <- 125 ## Finding the final reproductive number estimates with confidence intervals # NOTE should run with bootSamples > 10. rFinal <- estimateR(nbResults, dateVar = "infectionDate", indIDVar = "individualID", pVar = "pScaled", timeFrame = "months", rangeForAvg = c(cut1, cut2), bootSamples = 10, alpha = 0.05) ## Ploting the final result plotRt(rFinal, includeRtAvg = TRUE, includeRtCI = TRUE, includeRtAvgCI = TRUE)