Expand.Grid.R: A slight modification to expand.grid() such that when you pass data.frames in, the rows are kept together as tuples rather than being split apart

Expand.Grid.R

Expand.Grid<-function (..., stringsAsFactors = TRUE) 
{
    nargs <- length(args <- list(...))
    if (!nargs) 
        return(as.data.frame(list()))
    if (nargs == 0L) 
        return(as.data.frame(list()))
    Names <- function(x) {if(!is.null(names(x))) names(x) else rep("",length(x))}
    Paste <- function(...) {a<-list(...); r<-do.call("paste", c(list(sep="."),
        a[sapply(a, function(x) !is.character(x) || any(nzchar(x)))]));
        nx <- max(sapply(a, length))
        if (length(r)) return(rep(r, length.out=nx)) else return(rep("", nx))
    }
    contribcols <- sapply(args, function(x) ifelse(class(x)=="data.frame", ncol(x), 1))
    outargs <- sum(contribcols)
    cargs <- vector("list", outargs)
    nmc <- paste0("Var", seq.int(sum(contribcols)))
    nm <- unlist(lapply(seq_along(args), function(x) if(class(args[[x]])=="data.frame") {
        Paste(Names(args)[x], Names(args[[x]])) } else {Names(args)[x]}))
    if (is.null(nm)) 
        nm <- nmc
    else if (any(ng0 <- !nzchar(nm))) 
        nm[ng0] <- nmc[ng0]
    names(cargs) <- make.unique(make.names(nm))
    rep.fac <- 1L
    d <- sapply(args, function(x) ifelse(class(x)=="data.frame", nrow(x), length(x)))
    orep <- prod(d)
    if (orep == 0L) {
    	i<-1
        for (a in seq_along(args)) {
        	if (contribcols[a]==1) {
        		args[[a]]=list(a)
        	}
        	for(j in seq_len(contribcols[a])) {
        		cargs[[i]] <- args[[a]][[j]][FALSE]
        		i <- i+1
        	}
        }
    } else {	
    	i<-1
        for (a in seq_along(args)) {
            nx <- d[a]
            orep <- orep/nx
            x<-args[[a]]
            if (contribcols[a]==1) {
            	x<-list(x)
            }
            for(j in seq_len(contribcols[a])) {
            	y <- x[[j]]
            	y <- y[rep.int(rep.int(seq_len(nx), rep.int(rep.fac, 
                	nx)), orep)]
	            if (stringsAsFactors && !is.factor(y) && is.character(y)) 
    	            y <- factor(y, levels = unique(y))
        	    cargs[[i]] <- y
        	    i <- i+1
            }
            rep.fac <- rep.fac * nx
        }
    }
    rn <- .set_row_names(as.integer(prod(d)))
    structure(cargs, class = "data.frame", row.names = rn)
}

test.Expand.Grid.R

#same
expand.grid(height=seq(60,80,5), weight=seq(100,300,50), sex = c("Male","Female"))
Expand.Grid(height=seq(60,80,5), weight=seq(100,300,50), sex = c("Male","Female"))

#different
expand.grid(data.frame(a=c("ac","dc"), b=c("+","-")), g=1:3) #<-error
Expand.Grid(data.frame(a=c("ac","dc"), b=c("+","-")), g=1:3)

#different
Expand.Grid(a=c("ac","dc"), b=c("+","-"), g=1:3)
Expand.Grid(data.frame(a=c("ac","dc"), b=c("+","-")), g=1:3) #no ac/- or dc/+ combinations