3D array of indices of a 4D array

Hello everyone. I'm new to this forum.

I want to mask a 3D volume that changes over time (i.e. a 4D array) with a 3D binary mask, where 1 are in the positions that I want to keep and 0 the positions that I'm not interested in. Visually, they look more or less like this:

What I was trying is this:

% ´V´ is a width x height x depth x timePoints array, and ´mask´ is a width x height x depth array.
maskTime = repmat(mask,[1 1 1 timePoints]); % Repeat mask over time (size(maskTime) = width x height x depth x timePoints)
[X,Y,Z,T] = ind2sub(size(maskTime),find(maskTime==1)); % X,Y,Z and T are the positions in every dimension where there's a 1
maskedVolume = V(X,Y,Z,T);

However, when I run the code, I get the error: 'Requested array exceeds the maximum possible variable size.'

In my case, I have that the variables ´X´,´Y´, ´Z´ and ´T´ are:

And they contain all the indices where there's a 1. For example, in the case ´X´:

Here, we can see all the indices. Do you know how to fix this problem? I'm interested in avoiding for loops.

Thank you in advance.

[Asvin Kumar]

Could you share a minimum working example which reproduces your error?

Answer 1

[Matt J]

It should be sufficient just to do

maskTime=logical(maskedTime);

maskedVolume=V.*maskTime;

or possibly you were looking for

maskTime=logical(maskedTime);

maskedVolume=reshape(V,[],timePoints);

maskedVolume=maskedVolume(maskTime,:);