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## Re: How to get a matrix values' indices?

 From: Keith Goodman Subject: Re: How to get a matrix values' indices? Date: Tue, 28 Sep 2004 11:22:52 -0700

```> x
x =

1  2  3
1  2  2
1  1  3

> [i,j] = find(x==1);
> [i j]
ans =

1  1
2  1
3  1
3  2

> mean([i j])
ans =

2.2500  1.2500

>

On Tue, 28 Sep 2004 20:12:53 +0200, Mikolaj Karolczak
> Hello,
>
> Suppose we have a matrix of integer values. Is there any function to get
> quickly
> matrices of each value's indices?
>
> e.g.
>
> I have:
> [1 2 3
>  1 2 2
>  1 1 3]
>
> I want:
> -> 1: [1 1; 2 1; 3 1; 3 2]
> -> 2: [1 2; 2 2; 2 3]
> -> 3: [1 3; 3 3]
>
> Surely I can get it by checking the value for every index but for big matrices
> if works slowly.
>
> Actually I need to calculate the 'specific gravity' of each value in the
> matrix
> - the mean values of each value's indices. Maybe there is a function to do it
> yet simplier?
>
> Rgds,
> Mikolaj
>
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