R/events.R

In davidecannatanuig/openFaceR: A pacakge for the convenient analysis of OpenFace data

#' Count events.
#' @description Function to count how many differnet times a facial event occurs.
#' @param x the variable for which to count events (must have two levels: 0 and 1).
#' @param sensitivity how many frames might have the software missed and still considered the event as one.
#' @return The number of occurred events.
#' @examples
#' #Counting John blinkings
#' count_events(john$AU45_c)
#'
#' # Using a lower sensitivity to make sure each each blink is counted as one
#' count_events(john$AU45_c, sensitivity = 0)
#' # There will be higher risk of machine error
#'
#' @export

count_events <- function (x, sensitivity = 5) 
{
	if (!prod((levels(as.factor(x))) %in% c(0, 1))) {
		stop("You need to use a dychotomic variable with two levels: 0 and 1!")
	}
	count <- x[[1]]
	buffer <- 0
	for (i in 2:length(x)) {
		if (x[i] > x[i - 1]) {
			count <- count + 1
			buffer <- 0
		}
		else if (x[i] < x[i - 1] & buffer <= sensitivity) {
			x[i] <- 1
			buffer <- buffer + 1
		}
	}
	return(count)
}