R/redlist.R

In umatter/pvsR: Interact with the Project Vote Smart API for Scientific Research

# ' Reduce a nested list
# ' 
# ' A function that reduces a nested list containing some data frames in some of its elements (a list containing lists containing lists containing data frames...) by unlisting its elements (lists) until it only consits of a normal list containing the dataframes as elements.   
# ' @usage redlist(x)
# ' @param x a nested list containing some data frames
# ' @return a list containing data frames
# ' @examples
# ' a <- data.frame(a=c(1,2,4),b=c(5,5,6))
# ' b <- data.frame(a=c(3,4,5,6), b=c(8,8,5,4), c=c(9,4,2,1))
# ' l1 <- list(list(list(a,b)))
# ' redlist(x=l1)

redlist <-
	function (x) {

		n <- 0
		x. <- x
		# check how often the list has to be "unlisted" by the c function
		# n gives the number of do.calls of c until there's one component that is not any more a list.
		while (length(names(x.))==0) {
			x. <- do.call("c", x.)
			n <- n + 1
		}
		
		# if n is greater than 1 do.call c n-1 times to get the required list
		if (n>1) {
			for (i in 1:(n-1)) {
				x <- do.call("c", x)
			}
			return(x)
		} else {
			return(x)
		}
	}