Why won't my function in matlab changed the input matrix in the original code?

I am writing the code for a sudoku game. I am working on writing a function for the hint that will display another value for the user in one of the empty spaces in their sudoku matrix. However, when I run the function in the original code, the function changes it within its own code, but then in the main code, the matrix stays the same, and the value stays zero:

function mat = hint(mat,mat2) %input input is the usersudoku matrix and then mat2 is the original/correct and filled out sudoku matrix
vector = find(mat == 0); %find where user has no inputted values
l = length(vector); 
element = vector(randi([1,l],1)); %find random element
 num = mat2(element); 
mat(element) = num;  %set correct value in the user matrix from the base matrix to give user a hint
end

Here is how it is used in my main code:

case 5 % Hint 
hints = hints+1; % Increase hints variable to write to file 
hint(usersudoku, basesudoku) 
dispSudoku(usersudoku)

But in the main code, the usersudoku matrix doesn't change and I don't know why

Answer 1

[Walter Roberson]

usersudoku = hint(usersudoku, basesudoku);

Update in place does not happen just because a variable is updated in a function: the variable also has to be assigned to outside the function.

[Kayla Kloster]

I just realized that! Thanks so much!