How to pass Vector/Array to a symbolic function?

Question

I would like to pass an array or a vector to a symbolic function like this:

syms x y
rosenbrock(x, y) = 100 * (y - x^2)^2 + (1 - x)^2;

value = [0, -1];

rosenbrock(value)

but I can't find a way to do this. I have also tried to declare the input as []

rosenbrock([x, y]) = ...

but I'm still getting

Error using symfun/subsref (line 135) Symbolic function expected 2 inputs and received 1.

Answer 1

If you want to pass in an array, then the input arguments to your function need to be designed to handle an array:

syms x
rosenbrock(x) = 100*(x(2) - x(1)^2)^2 + (1 - x(1))^2;

value = [0, -1];
rosenbrock(value)

With a function like the one in your question, you need to pass in two arguments that correspond to the indices of the vector value :

syms x y
rosenbrock(x, y) = 100*(y - x^2)^2 + (1 - x)^2;

value = [0, -1];
rosenbrock(value(1), value(2))

This question isn't really specific to symbolic math – you would need to do the same thing for any Matlab function.

Answer 2

actually, I ran into similar issues where you would definitely NOT want to have to a) design your function to handle an array OR b) pass the expressions like:

rosenbrock(value(1), value(2))

the solution is this:

v = num2cell(value);
rosenbrock(v{:});