[R] Count number of rows in a matrix with a character pattern

[R. Michael Weylandt <michael.weylandt@gmail.com>]

I'd use a combination of rownames(), grepl() and sum(). 

Get the names with the first, test with the second and count the positives (by coercing TRUE -> 1) with the last

Michael

On Apr 29, 2012, at 3:46 PM, katarv <katiasmirn at gmail.com> wrote:

> Hi,
> 
> I have a large data set that I input as a matrix, where I have  1:x rows
> with names AX, then  x+1: y rows named AY, etc.  The idea is that I have to
> count how many rows exactly I have with name AX and how many I have with
> name AY (or find which row numbers have names AX). Is there any way in R to
> count a number of rows with a name matching a required pattern?
> 
> 
> Thanks in advance,
> 
> Katie 
> 
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