[R] read a matrix to find a value

[Phil Spector]

Judit -
     Does this example provide any insight?

> pop <- matrix(0,7,7)# Population matrix when t==0
> pop[sample(1:length(pop),1)] <-1 #Population matrix when t==1
> which(pop!=0,arr.ind=TRUE)
      row col
[1,]   3   4


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu


On Wed, 1 Dec 2010, Barroso, Judit wrote:

> Dear all of you,
>
> I would like if someone can help me to know how I can read a matrix looking for positions in the matrix that are not null.
> I have a matrix with most of the "cells" or "positions" null, I am trying to know the invasion power of a plant (number 1 in the matrix when t==1).
> I would like to continue the model writing some condition when the value of the matrix in not null, but I don't know what function or loop I have to use to find the values > than 0 for the next step.
>
> pop <- matrix(0,7,7)# Population matrix when t==0
> pop[sample(1:length(pop),1)] <-1 #Population matrix when t==1
>
> Thanks a lot,
> Judit
>
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>
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