Replacing elements of an array with a vector

I know that you can select elements out of a matrix that meet a condition and assign a new value, i.e.

    a = [1 2 3 4 5 6 7 9];
    a(a>4) = 0;
    a
        1  2  3  4  0  0  0  0  0

but what if you have a multidimensional matrix? I want to do something similar to the following:

    a = [1 2 3 4; 0 0 0 0];
    a(a(1,:)==1) = [a b];
    a
        a  2  3  4
        b  0  0  0

The situation is that I have a matrix where the first three dimensions are spatial and then there's a fourth that contains information about the spatial element. Right now, I'm using For loops to check every element and assign a vector [a b c d] to the spatial element. I would like to vectorize this and it's frustrating how easy it is to do this with one scalers, but it doesn't work with vectors.

[Laura Proctor]

Could you show what it is your starting with and what you would like to have as the result?

[Matt Fig]

I agree, make a real simple example of your actual data and show what you want to do. I am reading this as you have something like this:

A = round(rand(3,3,3,3)); % Sample data

and you want to find, say, all instances which match this:

V = squeeze(A(2,3,2,:))

along the fourth dimension and replace it with, say:

[4;5;6]

Is this close to what you want?

Answer 1

[Jesús Zambrano]

Hi Greggory,

According to the solution you show, you can get it by doing:

a(:, a(1,:)==1) = [a; b ]

Best regards,

Jesús