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

From: Guo Wei-Wei <wwguocn_at_gmail.com>
Date: Wed 31 May 2006 - 11:16:42 EST


Dear all,

I have a data.frame which has names as following.
[1] "XG1" "YG1" "XEST" "YEST"
[2] "XNOEMP1" "XNOEMP2" "YNOEMP1" "YNOEMP2"
[3] "XBUS10" "XBUS10A" "XBUS10B" "XBUS10C"
[4] "YBUS10" "YBUS10A" "YBUS10B" "YBUS10C"
[5] "XOWNBUS" "XSELFEST" "YOWNBUS" "YSELFEST"
Those columns have names beginning with "X" or "Y". Each "X" is paired by a "Y", e.g. "XG1" and "YG1", but they are not in the order of "X Y X Y ...". I want to combine "X*" and "Y*" like this:

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

How to choose columns by parts of names? For example, I can pick out XG1 and YG1 because they have the common part "G1".

Thank you.

Wei-Wei



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