[R] Counting zeros in a matrix

[Ben Fairbank]

rowSums((A[,1:8]==0)*A[,2:9]==1)

and adjust the 8 and the 9 for the number of columns in your matrix

Ben 

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Guenther, Cameron
Sent: Tuesday, November 28, 2006 3:20 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Counting zeros in a matrix

Hi All,

If you could help me with this problem I would greatly appreciate it.

Suppose I have a matrix A:

1 1 1 1 0 1 1 1 1
1 1 1 0 1 0 1 0 0
1 0 1 0 0 1 0 0 0
1 1 0 0 0 0 1 0 0

I would like, for each row, to sum the number of times a 0 appears in
front of a 1. So what I would like is to have
                   Sum
1 1 1 1 0 1 1 1 1   1
1 1 1 0 1 0 1 0 0   2 
1 0 1 0 0 1 0 0 0   2
1 1 0 0 0 0 1 0 0   1

I tried writing a function to do this but am getting mixed up in the
[i,j] coding.  This is just an example the real matrix is much larger.

Thanks in advance.



Cameron Guenther, Ph.D.
100 8th Ave. SE
St. Petersburg, Fl 33701
727-896-8626 ext. 4305
cameron.guenther at myfwc.com