R help - Feb 2008 - indices of rows containing one or more elements >0

Hi,

Given test <- matrix(c(0,2,0,1,3,5), 3,2)
> test[test>0]
[1] 2 1 3 5

These are values >0
> which(test>0)
[1] 2 4 5 6

These are array indices of those values >0
> which(apply(test>0, 1, all))
[1] 2

This gives the row whose elements are all >0

I can't seem to get indices of rows containing one or more elements >0

	[[alternative HTML version deleted]]

X <- matrix(c(0,2,0,1,0,0,3,5), ncol=2)

Informative version:
isPositive <- (X > 0)
nbrOfPositives <- apply(isPositive, MARGIN=1, FUN=sum)
hasPositives <- (nbrOfPositives >= 1)
positiveRows <- which(hasPositives)

Compact version:
positiveRows <- which(rowSums(X > 0) >= 1)

If you have an extremely large number of rows and only a few columns,
you might for speed purposes want to use an algorithm that iterates
over columns instead, but I leave that as an exercise.

/Henrik

On Feb 12, 2008 6:40 PM, Ng Stanley <stanleyngkl at gmail.com>
wrote:
> Hi,
>
> Given test <- matrix(c(0,2,0,1,3,5), 3,2)
>
> > test[test>0]
> [1] 2 1 3 5
>
> These are values >0
>
> > which(test>0)
> [1] 2 4 5 6
>
> These are array indices of those values >0
>
> > which(apply(test>0, 1, all))
> [1] 2
>
> This gives the row whose elements are all >0
>
> I can't seem to get indices of rows containing one or more elements
>0
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Is this what you are after?
> test <- matrix(c(0,2,0,1,3,5), 3,2)
> (x <- which(test > 0, arr.ind=TRUE))
     row col
[1,]   2   1
[2,]   1   2
[3,]   2   2
[4,]   3   2
> unique(x[, 'row'])
[1] 2 1 3
>

On Feb 12, 2008 9:40 PM, Ng Stanley <stanleyngkl at gmail.com>
wrote:
> Hi,
>
> Given test <- matrix(c(0,2,0,1,3,5), 3,2)
>
> > test[test>0]
> [1] 2 1 3 5
>
> These are values >0
>
> > which(test>0)
> [1] 2 4 5 6
>
> These are array indices of those values >0
>
> > which(apply(test>0, 1, all))
> [1] 2
>
> This gives the row whose elements are all >0
>
> I can't seem to get indices of rows containing one or more elements
>0
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

G'day Stanley,

On Wed, 13 Feb 2008 10:40:09 +0800
"Ng Stanley" <stanleyngkl at gmail.com> wrote:
> Hi,
> 
> Given test <- matrix(c(0,2,0,1,3,5), 3,2)
> 
> > test[test>0]
> [1] 2 1 3 5
> 
> These are values >0
> 
> > which(test>0)
> [1] 2 4 5 6
> 
> These are array indices of those values >0
> 
> > which(apply(test>0, 1, all))
> [1] 2
> 
> This gives the row whose elements are all >0
> 
> I can't seem to get indices of rows containing one or more elements
>0
which(apply(test>0, 1 any)) instead of which(apply(test>0, 1, all)) ??

HTH.

Cheers,

	Berwin

=========================== Full address ============================Berwin A
Turlach                            Tel.: +65 6516 4416 (secr)
Dept of Statistics and Applied Probability        +65 6516 6650 (self)
Faculty of Science                          FAX : +65 6872 3919       
National University of Singapore     
6 Science Drive 2, Blk S16, Level 7          e-mail: statba at nus.edu.sg
Singapore 117546                    http://www.stat.nus.edu.sg/~statba