Re: How to get a matrix values' indices?

[Quentin Spencer]

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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