#' Calculate grand average and individual peak amplitude and latency
#'
#' \code{p.measures} calculates local or simple peak amplitude and latency for each condition
#' in the data frame. Values are calculated for grand average waveforms, as well as
#' for each individual subject. Values are based on the electrode, or electrode cluster for
#' dense arrays, provided in \code{electrodes}.
#'
#' @param data A data frame in the format returned from \code{\link{load.data}}
#' @param electrodes A single value or concatenation of several values (to be averaged)
#' indicating which electrodes to include in generating the plot. At this time, if the
#' raw data files imported using \code{\link{load.data}}) do not have a header, you
#' must include a capital "V" in front of the number and enclose each electrode in quotes.
#' (For example, electrodes = "V78", or electrodes = c("V78", "V76").)
#' @param window The beginning and end points of a time window of interest; this is different
#' from the beginning and ending times \code{epoch.st} and \code{epoch.end} defined in
#' \code{\link{load.data}} (you only need to define the epoch once upon importing the data).
#' @param num.pts The number of bins to check for local peak measures. If no local peaks are
#' found, the simple peak will be returned. To force the simple peak, set \code{num.pts}
#' to 0.
#' @param pol The polarity of peaks to favor when multiple peaks are present. Entering
#' "pos" will locate the most positive peak. Entering "neg" will locate the most
#' negative peak. Entering "abs" will find the greatest deviation from 0, regardless
#' of the polarity (i.e., the absolute value). If a single peak is located, it will
#' be selected regardless of polarity specified. To avoid this, set \code{num.pts}
#' to 0 (for simple peak measures).
#'
#' @return A data frame with columns labeled:
#' \itemize{
#' \item Subject
#' \item Trial Type
#' \item Peak Latency
#' \item Peak Amplitude
#' }
#'
#' A plot indicating the time window and identified peak(s)
#'
#' @examples
#' # Calculate peak latency and amplitude
#' p.measures(ERPdata, electrodes = "V78", window = c(1000, 1500), num.pts=10, pol="abs")
#'
#' @author Travis Moore
p.measures <- function(data, electrodes, window, num.pts = 10, pol="abs") {
data.fun <- data
num.subs <- length(levels(data$Subject))
sub.IDs <- levels(data$Subject)
num.conditions <- length(levels(data$Stimulus))
trial.types <- levels(data$Stimulus)
time.points <- (length(data$Time)/num.subs)/num.conditions # an integer
# of the number of time points for one stimulus type for one subject
Time.range <- data$Time[1:time.points]
# only use this for grand average measures - for alternating stimulus blocks (old way)
stim.list <- vector("list")
for (i in 1:length(levels(data$Stimulus))) {
stim.list[[i]] <- c(rep(levels(data$Stimulus)[i], time.points))
}
Stimulus <- unlist(stim.list)
# only use this for independant measures
Stimulus.ind <- data$Stimulus
win1 <- window[1]
win2 <- window[2]
# calls the cluster function
cluster <- .cluster.seg(data, electrodes)
# calls the avg.sub function
avgsub <- .avg.subs(data, electrodes, window, cluster, Time.range, trial.types)
# extracts grand mean data
grand.avg <- .grand.average(data, electrodes, window, Time.range,
avgsub, trial.types, Stimulus, num.subs, num.conditions)
# vectors to hold peak measures
# ------------- starts with grand average measures
peaks.ga <- vector("list", num.conditions)
# these variables would not be necessary if peaks.ga collected the whole row
# but it was easier to program each piece of info for the data frame
for (t in 1:num.conditions) {
peaks.ga[[t]] = lapply(trial.types[t], grand.avg, Stimulus, Time.range,
win1, win2, num.pts, pol, FUN = .get.ga.pamps)
} # close for loop
unpacked.peaks.ga <- unlist(peaks.ga)
peak.ga.lat = vector("list", length(unpacked.peaks.ga))
peak.ga.cond = vector("list", length(unpacked.peaks.ga))
peaks.ga.cond = lapply(unpacked.peaks.ga, grand.avg, Stimulus, Time.range, win1, win2,
FUN = .get.peak.ga.cond)
peaks.ga.lat = lapply(unpacked.peaks.ga, grand.avg, Stimulus, Time.range, win1, win2,
FUN = .get.peak.ga.latency)
unpacked.peak.ga.cond <- unlist(peaks.ga.cond)
unpacked.peak.ga.lat <- unlist(peaks.ga.lat)
grand.peaks = setNames(data.frame("Grand Avg", unpacked.peak.ga.cond,
unpacked.peak.ga.lat, unpacked.peaks.ga),
c("Subject", "Trial Type", "Peak Latency", "Peak Amplitude"))
# ------------- begin individual measures
# make sure the lapply function is actually cycling through every subject
peaks = vector("list",num.conditions) # begin individual measures
for (i in 1:num.conditions) {
peaks[[i]] = lapply(sub.IDs, trial.types[i], avgsub, Stimulus.ind, Time.range,
win1, win2, num.pts, pol, FUN = .get.peak.amps)
} # close for loop
unpacked.peak.amp <- unlist(peaks)
peak.sub = vector("list", length(unpacked.peak.amp))
peak.cond = vector("list", length(unpacked.peak.amp))
peak.lat = vector("list", length(unpacked.peak.amp))
peaks.sub = lapply(unpacked.peak.amp, avgsub, Stimulus.ind, Time.range,
win1, win2, FUN = .get.peak.sub)
peaks.cond = lapply(unpacked.peak.amp, avgsub, Stimulus.ind, Time.range,
win1, win2, FUN = .get.peak.cond)
peaks.lat = lapply(unpacked.peak.amp, avgsub, Stimulus.ind, Time.range,
win1, win2, FUN = .get.peak.latency)
unpacked.peak.lat <- unlist(peaks.lat)
unpacked.peak.sub <- unlist(peaks.sub)
unpacked.peak.cond <- unlist(peaks.cond)
peaks.measures = setNames(data.frame(unpacked.peak.sub, unpacked.peak.cond,
unpacked.peak.lat, unpacked.peak.amp),
c("Subject", "Trial Type", "Peak Latency",
"Peak Amplitude")) # individual measures df
grandaverage(data, electrodes, window)
tryCatch(abline(v = unpacked.peak.ga.lat, lty = 6, col = c(2, 4, seq(5, num.conditions+3, 1))),
error = function(e) {abline(v = unpacked.peak.ga.lat, lty = 6, col = 2)}, silent = TRUE)
# binds both peak measures data frames and makes it available outside the function
peak.measures <- rbind(grand.peaks, peaks.measures)
return(peak.measures)
} # Function closing bracket
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.