[R] Better way than an ifelse statement?

[Joshua Wiley]

Hello All,

I am trying to create a column of weights based off of factor levels
from another column.  I am using the weights to calculate L scores.
Here is an example where the first column are scores, the second is my
"factor" and the third I want to be a column of weights.  I can do
what I want with an ifelse statement (see below), but I am wondering
if anyone knows of a cleaner way to do this?

example <- data.frame(cbind(rnorm(4), rep(1:4, 1), c(0)))

example$X3 <- ifelse(example$X2==1, -3, (
ifelse(example$X2==2, -1, (
ifelse(example$X2==3, 1, (
ifelse(example$X2==4, 3, NA))))))) ## this seems sloppy to me

> example
           X1 X2 X3
1  1.75308880  1 -3
2 -0.49273616  2 -1
3 -0.12446648  3  1
4 -0.06417217  4  3


Thanks for your help,

Joshua

-- 
Joshua Wiley
Senior in Psychology
University of California, Riverside
http://www.joshuawiley.com/