Evaluating a function at complex values

I am new to MATLAB and I am trying to evaluate a sybomlically defined function at complex values, but I get an error saying 'Array indices must be positive integers or logical values'. What should I change so that this works and outputs a complex value?

syms x
F = x^5-5*x^4-8*x^3+40*x^2-9*x+45;
P0 = 0+1i;
F(P0)

Answer 1

[Ameer Hamza]

F is a symbolic expression, not a symbolic function. You need to use subs()

syms x
F = x^5-5*x^4-8*x^3+40*x^2-9*x+45;
P0 = 0+1i;
subs(F, x, P0)

Following define F as symbolic function

syms x
F(x) = x^5-5*x^4-8*x^3+40*x^2-9*x+45;
P0 = 0+1i;
F(P0)

Answer 2

[Alan Stevens]

You need to make sure F is a function. For your particular function you don't need it to be symbolic:

>> F =@(x) x^5-5*x^4-8*x^3+40*x^2-9*x+45;
>> P0 = 2+0.5*i;
>> F(P0)

ans =

  87.3125 -11.4688i