Index exceeds the number of array elements. Index must not exceed 1

Question

I wanted to convert anonymous function to a symbolic function.

I have something like

f = @(x)4*(3/4*pi-x(1))-7*x(3)
g = sym(f)

but I always get Index exceeds the number of array elements. Index must not exceed 1. How to fix this?

My x has usually size 8,1 but that shouldn't be relevant i guess Do I need to convert my x to sym as well or?

Answer 1

In your anonymous function f, x is defined to have minimum three indices and hence sym(f) cannot be used to convert it to sym.

Instead, you can call f with a symbolic variable x of size 1x3 like this:

g = f(sym('x',[1,3]));

which gives:

>> g
g =
 3*pi - 7*x3 - 4*x1