# [R] Discarding a matrix based on the rowSums value

Juan Antonio Balbuena balbuena at uv.es
Mon Nov 21 16:58:04 CET 2011

```Hello
I would appreciate your help on the followig. I want to generate random
binary matrices but I need to discard those with all-1 rows. That is, for a
10x10 matrix with five 1's

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]    0    0    0    0    0    0    0    0    0     1
[2,]    0    0    0    0    0    0    1    0    0     0
[3,]    0    0    0    0    0    0    1    0    0     0
[4,]    0    0    0    0    0    0    0    0    0     0
[5,]    0    0    0    0    0    0    0    0    0     0
[6,]    0    0    0    0    0    0    0    0    0     0
[7,]    0    0    0    0    0    0    0    0    0     0
[8,]    0    0    0    0    0    0    0    0    0     0
[9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    0    0    0    0    1    1    0    0     0

would be passed on to further computations, whereas

[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,]    0    0    0    0    0    0    0    0    0    0
[2,]    0    0    0    0    0    0    0    0    0     0
[3,]    0    0    0    0    0    0    0    0    0     0
[4,]    0    0    0    0    0    0    0    0    0     0
[5,]    0    0    0    0    0    0    0    0    0     0
[6,]    0    0    0    0    0    0    0    0    0     0
[7,]    0    0    0    0    0    0    0    0    0     0
[8,]    0    0    0    0    0    0    0    0    0     0
[9,]    0    0    0    0    0    0    0    0    0     0
[10,]    0    1    0    1    0    1    1    0    0     1

For any N.1s <= Nrow, I am trying

Nrow = 10
Ncol = 10
N.1s = 5
flag <- TRUE
while (flag == TRUE) {
m <- matrix ((sample (c(rep(1, each=N.1s), rep(0,
each=((Ncol*Nrow)-N.1s))))), Nrow)
SUMROW <- rowSums(m)
if (SUMROW == N.1s) {flag <- TRUE} else {flag <- FALSE}
}
}

but I get this warning
Warning message:
In if (SUMROW == N.1s) { :
the condition has length > 1 and only the first element will be used

What I specifically need is a way to write "If any of the elements of the
SUMROW vector == N.1s then flag <-true else flag<-false".

Any help would be much appreciated.

--
View this message in context: http://r.789695.n4.nabble.com/Discarding-a-matrix-based-on-the-rowSums-value-tp4091995p4091995.html
Sent from the R help mailing list archive at Nabble.com.

```