Are Matlab Matrices transferred pass-by-value or pass-by-reference?

Question

I'm new at Matlab. You may find this question silly but I really wonder if the statement below is a pass-by-value operation or pass-by-reference operation.

I = imread('logo.png');
binaryImage = im2bw(I, 0.4);
Itemp = binaryImage;

Does the Itemp is a new matrix whose values are copied from binaryImage, or it is just a pointer to the binaryImage?

Answer 1

It's pass by reference, until you modify Itemp.

When you modify Itemp matlab will copy binaryImage to Itemp and then modify it.

I made some interesting tests a while a go. If you do:

A=rand(100);B=A;C=B;D=A;E=B;

only one copy is kept in memory. If you modify A

A(1)=1;

Then, matlab make one new copy of the matrix for the new A, and the variables B,C,D,E still point to the matrix of the old A.