Moving columns within a data.frame() without retyping

Question

Is there a method for moving a column from one position in a data.frame to the next - without typing an entirely new data.frame()

For example:

a <- b <- c <- d <- e <- f <- g <- 1:100 df <- data.frame(a,b,c,d,e,f,g) 

Now let's say I wanted "g" in front of "a"

I could retype it, as

df <- data.frame(g,a,b,c,d,e,f) 

But is there not a quicker way? (Imagine 1500+ columns)

Answer 1

The subset function has a nice select argument that gives a convenient way to select ranges of columns by name:

df <- subset(df, select=c(g,a:f)) 

Answer 2

I wrote this function recently called moveme. It's designed to work on vectors, with the intent of shuffling column orders around.

Here's the function:

moveme <- function (invec, movecommand) {   movecommand <- lapply(strsplit(strsplit(movecommand, ";")[[1]],                                   ",|\\s+"), function(x) x[x != ""])   movelist <- lapply(movecommand, function(x) {     Where <- x[which(x %in% c("before", "after", "first",                                "last")):length(x)]     ToMove <- setdiff(x, Where)     list(ToMove, Where)   })   myVec <- invec   for (i in seq_along(movelist)) {     temp <- setdiff(myVec, movelist[[i]][[1]])     A <- movelist[[i]][[2]][1]     if (A %in% c("before", "after")) {       ba <- movelist[[i]][[2]][2]       if (A == "before") {         after <- match(ba, temp) - 1       }       else if (A == "after") {         after <- match(ba, temp)       }     }     else if (A == "first") {       after <- 0     }     else if (A == "last") {       after <- length(myVec)     }     myVec <- append(temp, values = movelist[[i]][[1]], after = after)   }   myVec } 

Usage is simple. Try these out:

moveme(names(df), "g first") moveme(names(df), "g first; a last; e before c") 

Of course, using it to reorder the columns in your data.frame is straightforward:

df[moveme(names(df), "g first")] 

And for data.tables (moves by reference, no copy) :

setcolorder(dt, moveme(names(dt), "g first")) 

---

The basic options are:

• first
• last
• before
• after

Compounded moves are separated by a semicolon.