MATLAB function doesn't work despite its script works fine

Question

This function returns the error Not enough input arguments.

function numgrad = computeNumericalGradient(J, theta)

SIZE=length(theta);
numgrad = zeros(SIZE,1);
perturb = zeros(SIZE,1);
e = 1e-4;
for p = 1:SIZE
    % Set perturbation vector
    perturb(p) = e;
    loss1 = J(theta - perturb);
    loss2 = J(theta + perturb);
    % Compute Numerical Gradient
    numgrad(p) = (loss2 - loss1) / (2*e);
    perturb(p) = 0;
end

end

When I pass J and theta as follows:

function db = f(X)
db=X'*X;
end

theta=[1; 2; 3];

However this script runs fine.

theta=[1; 2; 3];

SIZE=length(theta);
numgrad = zeros(SIZE,1);
perturb = zeros(SIZE,1);
e = 1e-4;
for p = 1:SIZE
    % Set perturbation vector
    perturb(p) = e;
    loss1 = f(theta - perturb);
    loss2 = f(theta + perturb);
    % Compute Numerical Gradient
    numgrad(p) = (loss2 - loss1) / (2*e);
    perturb(p) = 0;
end

This is how I am calling my function.

theta=[1; 2; 3];
computeNumericalGradien(f,theta)

I do not understand how does the script work given that the only difference in the script and function is that the function and its argument are not arbitrary in the script.

PS: I am using MATLAB 2014

You haven't shown how you're calling your function when it throws the error. Or the full error... — sco1, May 25 '16 at 15:42
You need to pass f as an anonymous function, you are calling it with no inputs, hence the error — sco1, May 25 '16 at 15:44
@excaza I have edited my question to include the way I am calling my function. — Tom, May 25 '16 at 15:44
You are simply passing a function to the function input , the function f itself requires an X input which is missing , better call the function f inside and pass X through the input — Novice_Developer, May 25 '16 at 15:46
Unfortunately, you can't pass functions like that in MATLAB (use Python for that). If you really want to pass a function, use a function handle: `function_you_are_calling(@f,...` — Andras Deak -- Слава Україні, May 25 '16 at 15:50
@AndrasDeak Okay I shall see the documentation for function handle. Can you explain why am I getting *Not enough input arguments* error specifically? — Tom, May 25 '16 at 15:56
Because in newer versions of MATLAB, writing `f` is equivalent to `f()`, which is a zero-input-argument form of a function. — Andras Deak -- Слава Україні, May 25 '16 at 15:56
Ok Thanks, if you wish to post it as an answer, I would accept it. — Tom, May 25 '16 at 16:00
I think this is a simple typo problem, which is unlikely to help future readers. This is the reason I didn't give a full answer, only comment. I suggest that you consider deleting your question. — Andras Deak -- Слава Україні, May 25 '16 at 16:04
@AndrasDeak I don't agree. It highlights that saved/local functions are not passed as objects, which isn't particularly clear in the documentation. I think it's beneficial, though I wouldn't be surprised if there's a duplicate somewhere. — sco1, May 25 '16 at 16:06

MATLAB function doesn't work despite its script works fine

0 Answers0