On Jul 16, 2011, at 9:55 AM, Thomas Chesney wrote:
I know there's a really easy way to do this but I just can't track
it down. I experimented with various apply functions but couldn't
get it quite right.
I have a matrix like this:
1, 16
1, 23
1, 21
1, 6
1, 25
2, 4
2, 17
2, 45
2, 11
2, 20
tapply(mtx[,2], mtx[,1], max)
and I'd like to find the max value in Column 2 (or the index to the
max value) grouped by the first column. So the max for Group 1, the
max for Group 2 etc.
Any help would be appreciated.
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David Winsemius, MD
West Hartford, CT
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
