[R] Discarding a matrix based on the rowSums value

[David Winsemius]

On Nov 21, 2011, at 10:58 AM, Juan Antonio Balbuena wrote:

> 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
> must be discarded.

Why? it has no rows that meet your verbal description " all-1  
rows" (Nor it would meet your code implementation below, but I offer a  
suggestion in case you want only to exclude matrices with exactly rows  
whose sum is 5 but would accept those with sums of 4, or 6, etc.)

>
> 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}

rowSums retruns a vector, whereas if() only works with vectors of  
length 1.

Perhaps you want:

flag <-  ifelse(SUMROW == N.1s, TRUE, 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.
>
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David Winsemius, MD
West Hartford, CT