Extracting Non-Zero Values From Array and Applying to a Different Matrix

I have two 1 x n arrays, call them p = [p_1,..., p_n] and phi = [phi_1,...,phi_n]. It is possible that p will have zero values, and I would like to extract the nonzero values into a separate array, call it workingP. At the same time, for each nonzero value p_k, I would like to include phi_k in a second new array, workingPhi.

So ultimately, I will end up with workingP = {[p_k] : p_k ~= 0} and workingPhi = {[phi_k] : p_k ~= 0} where k ranges from 1 to n.

I'm not sure how to go about this without reallocating memory over and over again.

Answer 1

[Guillaume]

tokeep = p ~= 0;   %logical array indicating which elements to keep
workingP = p(tokeep);
workingPhi = phi(tokeep);

Answer 2

[Matt J]

[~,idx,workingP] = find(p);
workingPhi = phi(idx);