R/extract.turnogram.R

In pastecs: Package for Analysis of Space-Time Ecological Series

"extract.turnogram" <-
function(e, n, level=e$level, FUN=e$fun, drop=0, ...) {
	if (missing(n)) n <- NULL
	data <- as.ts(eval(parse(text=e$data)))
	data <- window(data, start=start(data) + drop)
	if (level == 1) {	# Simply return the original time series
		res <- data
	} else {
		if (is.null(n) || n > length(data)) n <- length(data)

		# Check the validity of level
		if (level < 1 || level > n/3) stop("level must be a value between 1 and n/3!")
		res <- aggregate(data, nfrequency=frequency(data)/level, FUN=FUN)
	}
	if (NROW(res) < 10)
		warning("The extracted series contains very few data (n < 10)")
	res
}