Problem with eval and symbolic inequation

I am trying to calcendulate the equation below in the manner and I can not.

syms t
syms joelho(t)
joelho(t) = ((0.15*sin(5*pi*t - pi/2) + 0.15)*heaviside(t)*(t<0.4) + (0.53625*sin(10*pi*t/3 + pi/6) + 0.53625)*heaviside(t - 0.4))*180/pi;
t = 0;
s = eval(t);

The following error appears:

Undefined function 'eval' for input arguments of type 'double'.
Error in teste4 (line 8)
s = eval(t);

the result is zero.

[Mischa Kim]

What exactly are you trying to do? Evaluate joelho(t) at t = 0 ?

Answer 1

[Mischa Kim]

Anna, try

syms t
joelho =    ((0.15*sin(5*pi*t - pi/2) + 0.15)*heaviside(-t - 0.4) + ...
  (0.53625*sin(10*pi*t/3 + pi/6) + 0.53625)*heaviside(+t - 0.4))*180/pi;

s = subs(joelho,t,0)   % evaluate expression at t = 0
ezplot(joelho,[-2,2])  % plot