R/createTimeSlices.R

In bplloyd/CoreHF: What the package does (short line)

# RETURNS TIME SLICES FOR ROLLING LISTS
createTimeSlices = function(data, initialWindow = 12, fixedWindow = TRUE, forward = F, on = "months"){
  y = 1:nrow(data)
  stops <- (seq(along = y))[initialWindow:length(y)]
  if (fixedWindow){
    starts <- stops - initialWindow + 1
  }
  else{
    starts <- rep(1, length(stops))
  }
  slices = lapply(mapply(seq, starts, stops, SIMPLIFY = FALSE), function(x)return(zoo::index(data)[x]))
  if(!forward)
    names(slices) = zoo::index(data[initialWindow:nrow(data),])
  if(forward)
    names(slices) = zoo::index(data[1:(nrow(data)-initialWindow+1)])
  thin <- function(x, skip = 2){
    n <- length(x)
    x[seq(1, n, by = skip)]
  }

  epoints = as.character.Date(zoo::index(data)[xts::endpoints(data, on = on)])
  slices = slices[which(names(slices) %in% epoints)]
  # if (skip > 0){
  #   slices <- thin(slices, skip = skip + 1)
  # }
  return(slices)
}