An easy way to achieve this is to create a scalar variable and then to gradually increase the size over time while you execute the code. For example, if you wish to store the value of 'Var_A' after each iteration (with respect to time in this case) you can concatenate the new values over time and create a 1-D array. i,e
Arr=0;
for i=1:n
% Various operations your function performs. Var_A gets updated here
Arr(i)=Var_A;
end
'Arr' will contain the required values which you can plot with respect to time.
Note: This approach is however not recommended if 'n' is a large value as this leads to repeated reallocation of memory by MATLAB. You can go through the following link for more information: https://in.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html
A alternative method which is more efficient would be to initialize the array/vector beforehand and populating the initialized array during execution. If you know how many elements the vector will contain after execution, you can initialize the vector.