initial checkin (v0.3)

vcomb.R

@@ -0,0 +1,42 @@
+##' combine all possible pairs of vectors \code{v1} and \code{v2}
+##' using function \code{myfun}
+##'
+##' In essence, this is a generalized version of \code{\link[base]{outer}}
+##' allowing non-scalar return values for \code{myfun}.
+##'
+##' Possible extensions:
+##' \enumerate{
+##' \item reformat the output to be matrix-like (see outer)
+##' \item use a list of index pairs with \code{lapply} to allow
+##'       irregular return values
+##' \item shuffle the order of elements (incompatible with (1))
+##' }
+##' @title vector combine
+##' @param v1 first vector
+##' @param v2 second vector
+##' @param myfun function to combine the element pairs from the two vectors
+##' @param ... not used
+##' @return vector (or matrix, array) of combinations
+##' @author Benno Puetz \email{puetz@@mpipsykl.mpg.de}
+##' @examples
+##' a <- 1:3
+##' b <- 5:9
+##' vcomb(a, b)
+vcomb <- function(v1, v2, myfun = c, ...){
+    mat <- matrix(as.numeric(unlist(strsplit(outer(seq_along(v1),
+                                                   seq_along(v2),
+                                                   FUN = function(a, b){
+                                                       paste(a, b,
+                                                             sep = '.')
+                                                   }),
+                                             '.',
+                                             fixed = TRUE)
+                                    )),
+                  ncol = 2,
+                  byrow = TRUE)
+    combine.vectors <- function(rv) {
+        retval <- myfun(v1[rv[1]], v2[rv[2]])
+        return(retval)
+    }
+    return(apply(mat, 1, combine.vectors))
+}