R/list2adjmat.R

In drmjc/mjcbase: General helper functions for dealing with \R objects/data types

#' Convert a list to an adjacency matrix
#' 
#' If x is a list of variably lengthed vectors, then return a table which has
#' the
#' unique values as the rownames, and the names(x) as the colnames, with either
#' a 0 or 1
#' depending on whether the entity in row i was found in the vector in column
#' j. Sorted by
#' decreasing frequency across the list of vectors (ie row 1 contains the word
#' that was
#' found in the most number of vectors in list x)
#' 
#' @param x a named list, where each element is a character vector. If it's
#'   unnamed, names will be assigned
#' @return a data.frame of 0 or 1, where rows correspond to unique words,
#'   columns represent each list element.
#' @author Mark Cowley, 2009-10-29
#' @export
#' 
#' @examples
#' mylist <- list(A=letters[1:15], B=letters[10:26], C=letters[15:20])
#' list2adjmat(mylist)
#' 
list2adjmat <- function(x) {
	counts <- sort(table(unlist(x)), decreasing=TRUE)
	res <- as.data.frame(matrix(0,length(counts), length(x)), stringsAsFactors=FALSE)
	dimnames(res) <- list(names(counts), names(x))
	
	for(i in 1:length(x)) {
		idx <- match(x[[i]], names(counts))
		res[idx,i] <- 1
	}
	res
}