Here is my problem in a small bit of code used as an example, trial(0) function [] = trial(test) disp(test) if(test == 1) disp('test is one') test = 0; end disp(test) Matlab prints out this: 0 'test is one' 0 This is not my real code, there are over 500 lines of it, but this is a section of my code where the problem has risen. I have used the search function to see if I have been incrementing any variables anywhere, and have put in over 2 hours trying to see why MATLAB is changing my variables when I don't want it to.