Pivoting rows into columns

Question

Suppose (to simplify) I have a table containing some control vs. treatment data:

Which, Color, Response, Count
Control, Red, 2, 10
Control, Blue, 3, 20
Treatment, Red, 1, 14
Treatment, Blue, 4, 21

For each color, I want a single row with the control and treatment data, i.e.:

Color, Response.Control, Count.Control, Response.Treatment, Count.Treatment
Red, 2, 10, 1, 14
Blue, 3, 20, 4, 21

I guess one way of doing this is by using an internal merge on each control/treatment subset (merging on the Color column), but is there a better way? I was thinking the reshape package or the stack function could somehow do it, but I'm not sure.

Answer 1

Using the reshape package.

First, melt your data.frame:

x <- melt(df) 

Then cast:

dcast(x, Color ~ Which + variable)

Depending on which version of the reshape package you're working with it could be cast() (reshape) or dcast() (reshape2)

Voila.