time since event and decaying cumulative sums for binary time series

decay.R

decay <- function(yvar, d) {
  # yvar: a binary variable
  # d: number of periods
  # returns: the cumulative sum of yvar at each point
  # where each addition to the count decays away after d periods
  yvar[is.na(yvar)] <- 0
  run <- cumsum(yvar)
  tvar <- seq_along(yvar)
  run <- 0
  sum <-  0
  for(i in 1:length(tvar)) {
	if(yvar[i] == 1)
	  run <- run + 1
	if(run != 0) {
	  event.idx <- which(yvar == 1)
	  for(j in 1:length(event.idx)) {
		if(i == (d + event.idx[j]))
		  run <- run - 1
		}}
	sum[i] <- run
  }
  return(sum)
}

tse.R

tse <- function(yvar, tvar = seq_along(yvar)) {
   if (!(is.numeric(yvar) | is.logical(yvar))){
        stop("yvar must be either numeric or logical")
    }
   yvar[is.na(yvar)] <- 0
   event.idx <- which(yvar == 1) #Find index positions for events
   run <- cumsum(yvar) #calculate sum up until each index point, returns vector
   un <- unique(run) #unique values of run variable
   tlist <- list()
   for (i in 1:length(un)){ #loop over unique values of run
     v <- un[[i]]
     y <- yvar[run == v]
     t <- tvar[run == v]
     t <- t - t[1]
     tlist[[i]] <- t
   }
   timeAfterEvent <- unlist(tlist)
   timeAfterEvent[run == 0] <- NA
   run[run == 0] <- NA
   return(timeAfterEvent)
 }