Input Argument Undefined for Passing a Parameter to a Function

Hello,

I apologize if I am asking a very simple question but it's been something that I have been trying to work out and so far have been unsuccesful.

I am trying to write code to employ the gradient descent method on the camel function. Displayed below is the code:

Gradient Descent:

function [ dx ] = grad_d(v,f,gamma )

[Fx, Gx, Hx]= f(v);

dx = A - gamma*Gx;

end

In this case I want to use the function 'camel':

function [ Fx, Gx, Hx ] = camel(vec)

V = num2cell(vec);
[x,y] = V{:};

Fx = 2*x^2 - 1.05*x^4 + (x^6/6) + x*y+y^2;
Gx = [ x^5 - (21/5)*x^3 + 4*x + y; 
    x+2*y];
Hx = [ 5*x^4 - (63/5)*x^2 + 4, 1;
            1, 2];

end

When I try to run one evaluation with the above code I get the error below:

I run the code as follows:

vec = ones(2,1)
grad_d(vec,camel,.1)

and receive the following:

 _Input argument "vec" is undefined._

I know that I am overlooking something small but I can't pin it down. Any help would be much appreciated.

Thank you,

Answer 1

[Image Analyst]

Well you wrote the function to take in vec. What values do you want to pass in for it? You have to assign them. It can't read your mind.

[Peter]

Hi Image Analyst,

I completely understand your response - I made a mistake when copying over the command line codes above. I have vec as the vector of ones and get the issue I initially mentioned.

Thanks again.

[James Tursa]

@Peter: Do you still have this line:

grad_d(vec,camel,.1)

The 2nd argument is camel. That will call the function camel without any input arguments to camel. Then when it gets inside the camel function and tries to use the variable vec, you get the error.

[Image Analyst]

Don't pass in camel (If you did you'd have to use a @ in front of it).

vec = ones(2,1)
grad_d(vec,.1) % Call it without camel

Just call camel() inside the function:

function dx = grad_d(v,gamma)
[Fx, Gx, Hx]= camel(v);
dx = A - gamma*Gx;
end

Answer 2

[Peter]

Hello,

I am still having this problem. I made a more simple function:

function [ fin] = testfunction( vec )
V = num2cell(vec);
[x,y] = V{:};
fin = x+y;
end

If I try to call it using feval I get the same error. Any other thoughts on this? I am sure that it is a very trivial problem but I don't see what it is.

Thanks again