Message-ID: <e40d78ce0905051600x29674ca0q5361343c7d4402c8@mail.gmail.com>
Date: 2009-05-05T23:00:29Z
From: Mark
Subject: Relative subscripts?
Dear R-helpers,
I have a dataframe with several columns, one of which is called LENGTH.
I would like to make a new column called DIFF containing the value of
LENGTH minus LENGTH in the previous row, like this:
ID LENGTH DIFF
1 1 10 NA
2 2 15 5
3 3 20 5
4 4 12 -8
5 5 18 6
I'd like to think there are "relative subscripts" in R but I can't
find any reference to such a thing.
Any help solving this problem would be much appreciated, thanks!
Mark Na