Rearange data frame in R

Question

I have a data.frame in R that looks like this:

df <- data.frame(date=c(1,2,1,2), id=c(11,11,22,22), x=c(1,2,3,4))

But I want to rearrange it with a two new columns (depending on which id is considered) as

df2 <- data.frame(date=c(1,2),x1=c(1,2),x2=c(3,4))

How can do it? What is the general approach to such tasks?

Answer 1

Using reshape.

reshape(df, direction="wide", timevar="id", idvar="date")
#   date x.11 x.22
# 1    1    1    3
# 2    2    2    4