Why the user-defined function return an empty matrix when there is a division formula about global variables?

Question

Zhang Gene 2020-5-1

评论： Zhang Gene 2020-5-3

Here is my code:

function ans = rho_free(xm)
    global m ;%Where m = 1 is defined in the first few lines
    ans = xm./m;
end

I've put this part of code at the end of the document, and defined

m = 1;

at the very begining of the same document.

When I call the function rho_free(2), I get an empty matrix. And I don't know why and have no idea how to solve this problem.

Thank

Answer 1

Mehmed Saad 2020-5-1

You need to define

global m

before calling the function rho_free. if global m is not defined m will be empty

the best way is

global m
m = 1
rho_free(2)
ans =
     2

On the other hand if (clear all) is applied at the start of the code, global variable will be cleared (and last value is not retained)

Now suppose i directly call rho_free without initializing global m ( considering it has no value before) then

rho_free(2)
ans =
     []

Zhang Gene 2020-5-3

Thanks!