MATLAB Language Common mistakes and errors Do not name a variable with an existing function name
Example
There is already a function sum(). As a result, if we name a variable with the same name
sum = 1+3;
and if we try to use the function while the variable still exists in the workspace
A = rand(2);
sum(A,1)
we will get the cryptic error:
Subscript indices must either be real positive integers or logicals.
clear() the variable first and then use the function
clear sum
sum(A,1)
ans =
1.0826 1.0279
How can we check if a function already exists to avoid this conflict?
Use which() with the -all flag:
which sum -all
sum is a variable.
built-in (C:\Program Files\MATLAB\R2016a\toolbox\matlab\datafun\@double\sum) % Shadowed double method
...
This output is telling us that sum is first a variable and that the following methods (functions) are shadowed by it, i.e. MATLAB will first try to apply our syntax to the variable, rather than using the method.
