# Re: [R] help: how to get the position of a value in a matrix

From: Liaw, Andy <andy_liaw_at_merck.com>
Date: Thu 14 Jul 2005 - 09:33:48 EST

Use which(..., arr.ind=TRUE); e.g.,

> m <- matrix(runif(12), 3, 4)
> which(m > .8, arr.ind=TRUE)

row col

```[1,]   1   3
[2,]   2   3
[3,]   3   3
[4,]   3   4

> m
[,1]       [,2]      [,3]      [,4]
[1,] 0.2148183 0.08251853 0.9444718 0.4487148
```
[2,] 0.5386863 0.49673282 0.8054240 0.5101593 [3,] 0.6252847 0.70974516 0.8858951 0.8590655

Andy

> From: wu sz
>
> Hello,
>
> I have a data set matrix of 1200 * 15. How can I get the position of a
> specific value in the matrix?
>
> I use "seq(along = x)[x > value]" to look for the position of the
> value in the matrix, but "seq" can just find the sequence position row
> by row in the matrix, not a real position (like "rowNumber,
> colNumber"). Is any function for that?
>
> Thank you,
> Shengzhe
>
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