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

 From: Quentin Spencer Subject: Re: How to get a matrix values' indices? Date: Tue, 28 Sep 2004 13:26:22 -0500 User-agent: Mozilla Thunderbird 0.8 (X11/20040913)

```You're looking for the "find" function, as in this example:

octave:1> x=[1,2,3;1,2,2;1,1,3];
octave:2> [ii,jj]=find(x==1);
octave:3> [ii,jj]
ans =

1        1
2        1
3        1
3        2

Mikolaj Karolczak wrote:

```
```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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```
```

-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

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```