I have a large array and would like to extract from it the row and column indices just of values for which a particular boolean condition is true. I assume there's a simple way to do this, but I haven't figured it out yet. Any help would be appreciated. Tim
basic array question
3 messages · Tim Alcon, Uwe Ligges, PIKAL Petr
Tim Alcon wrote:
I have a large array and would like to extract from it the row and column indices just of values for which a particular boolean condition
Do you mean a matrix, i.e. exactly 2 dimensions?
is true. I assume there's a simple way to do this, but I haven't figured it out yet. Any help would be appreciated.
Example: X <- matrix(1:9, 3) col(X)[X == 4] row(X)[X == 4] Uwe Ligges
Tim
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Hi
On 2 Jun 2006 at 10:26, Uwe Ligges wrote:
Date sent: Fri, 02 Jun 2006 10:26:44 +0200 From: Uwe Ligges <ligges at statistik.uni-dortmund.de> Organization: Fachbereich Statistik, Universitaet Dortmund To: Tim Alcon <talcon at iastate.edu> Copies to: r-help at stat.math.ethz.ch Subject: Re: [R] basic array question
Tim Alcon wrote:
I have a large array and would like to extract from it the row and column indices just of values for which a particular boolean condition
Do you mean a matrix, i.e. exactly 2 dimensions?
is true. I assume there's a simple way to do this, but I haven't figured it out yet. Any help would be appreciated.
Example: X <- matrix(1:9, 3) col(X)[X == 4] row(X)[X == 4]
or
which(X==4, arr.ind=T)
row col [1,] 1 2
which works on higher dim arrays too
X <- array(1:12, c(3,2,2))
X
, , 1
[,1] [,2]
[1,] 1 4
[2,] 2 5
[3,] 3 6
, , 2
[,1] [,2]
[1,] 7 10
[2,] 8 11
[3,] 9 12
which(X==6, arr.ind=T)
dim1 dim2 dim3 [1,] 3 2 1
HTH Petr
Uwe Ligges
Tim
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Petr Pikal petr.pikal at precheza.cz