apply <- function(X, MARGIN, FUN, ...) { FUN <- match.fun(FUN) ## Ensure that X is an array object d <- dim(X) dl <- length(d) if(dl == 0) stop("dim(X) must have a positive length") ds <- 1:dl if(length(oldClass(X)) > 0) X <- if(dl == 2) as.matrix(X) else as.array(X) dn <- dimnames(X) ## Extract the margins and associated dimnames s.call <- ds[-MARGIN] s.ans <- ds[MARGIN] d.call <- d[-MARGIN] d.ans <- d[MARGIN] dn.call<- dn[-MARGIN] dn.ans <- dn[MARGIN] ## dimnames(X) <- NULL ## do the calls d2 <- prod(d.ans) if(d2 == 0) { ## arrays with some 0 extents: return ``empty result'' trying ## to use proper mode and dimension: ## The following is still a bit `hackish': use non-empty X newX <- array(vector(typeof(X), 1), dim = c(prod(d.call), 1)) ans <- FUN(if(length(d.call) < 2) newX[,1] else array(newX[,1], d.call, dn.call), ...) return(if(is.null(ans)) ans else if(length(d.ans) < 2) ans[1][-1] else array(ans, d.ans, dn.ans)) } ## else newX <- aperm(X, c(s.call, s.ans)) dim(newX) <- c(prod(d.call), d2) ans <- vector("list", d2) if(length(d.call) < 2) {# vector if (length(dn.call)) dimnames(newX) <- c(dn.call, list(NULL)) for(i in 1:d2) { tmp <- FUN(newX[,i], ...) if(!is.null(tmp)) ans[[i]] <- tmp } } else for(i in 1:d2) { tmp <- FUN(array(newX[,i], d.call, dn.call), ...) if(!is.null(tmp)) ans[[i]] <- tmp } ## answer dims and dimnames ans.list <- is.recursive(ans[[1]]) l.ans <- length(ans[[1]]) ans.names <- names(ans[[1]]) if(!ans.list) ans.list <- any(unlist(lapply(ans, length)) != l.ans) if(!ans.list && length(ans.names)) { all.same <- sapply(ans, function(x) identical(names(x), ans.names)) if (!all(all.same)) ans.names <- NULL } len.a <- if(ans.list) d2 else length(ans <- unlist(ans, recursive = FALSE)) if(length(MARGIN) == 1 && len.a == d2) { names(ans) <- if(length(dn.ans[[1]])) dn.ans[[1]] # else NULL return(ans) } if(len.a == d2) return(array(ans, d.ans, dn.ans)) if(len.a > 0 && len.a %% d2 == 0) { if(is.null(dn.ans)) dn.ans <- vector(mode="list", length(d.ans)) dn.ans <- c(list(ans.names), dn.ans) return(array(ans, c(len.a %/% d2, d.ans), if(!all(sapply(dn.ans, is.null))) dn.ans)) } return(ans) }