[R] gettng the row number based on column conditions

[Joshua Wiley]

Hi,

You should use the logical "and", i.e., "&" to tell R that you need
condition 1 (first column equals 1) AND condition 2 (second column
equals 1) to be true:

which(X[, 1] == 1 & X[, 2] == 1)

HTH,

Josh

On Sun, Nov 14, 2010 at 12:39 AM, gtg <maifeng at gmail.com> wrote:
>
> Hi all, I would like to get the row numbers in X where col1 and col2 are both
> 1
> I tried this:
> which(X[,c(1,2)]==1)
> but it gives me the row numbers where either col1 or col2 = 1
>
> What should I do? Thank you.
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/