How to return a array into a matrix index in matlab

Question

Here is what I have:

coluna = zeros(2,3);
coluna(1) = func(3,2,1);
coluna(2) = func(3,4,5);

Here is example of the function:

function vec = func(a,b,c)
    vec = zeros(3,1);
    vec(1,1) = a*b*c;
    vec(2,1) = a+b+c;
    vec(3,1) = a-b-c;
end

This is only an example code, but it illustrate pretty much everything I mean by the problem.

In C++ lets say it would be like this:

int *func(int a,int b,int c){
    int vet[2];
    vet[0]=a*b*c;
    vet[1]=a+b+c;
    vet[2]=a-b-c;
    return vet;
}

int main(){
    int mat[1][2];
    mat[0]=func(3,2,1);
    mat[1]=func(3,4,5);
}

In MatLab it will give me this error:

In an assignment A(I) = B, the number of elements in B and I must be the same.

How may I fix this?

Fantastic Mr Fox · Accepted Answer · 2014-09-18 22:50:19Z

1

The reason this occurs is because you are doing this:

coluna(1) = ...

When you want to assign a row of an array you need to do this:

coluna(1, :) = ...

similarly for a column:

 coluna(:, 1) = ...

Then you need to make sure the return from func is the same size as the thing you are replacing.

So in your example, this is the correct way to assign the output from func:

coluna = zeros(2,3);
coluna(1, :) = func(3,2,1);
coluna(2, :) = func(3,4,5);

answered Sep 18, 2014 at 22:50

Fantastic Mr Fox

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