[R] How to choose columns in data.frame by parts of columns' names?

[Guo Wei-Wei]

Gabor and Peter,

Thank you. Both of you give me excellent ways. I have a further problem.

How can I get the common parts of column names as column names in a
new data.frame? For example, I combines data of XG1 and YG1 in
data.old and get a new column in data.new named G1. Can It be done
automaticlly?

 data.new[,"G1"]  <- (data.old[,"XG1"] + data.old[,"YG1"])/2


2006/5/31, Gabor Grothendieck <ggrothendieck at gmail.com>:
> This is not restricted to single matches:
>
> > colnames(iris)
> [1] "Sepal.Length" "Sepal.Width"  "Petal.Length" "Petal.Width"  "Species"
> > regexpr("Sepal", colnames(iris)) > 0
> [1]  TRUE  TRUE FALSE FALSE FALSE
>