Conversion to double from sym is not possible

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Tyler
Tyler on 14 Nov 2011
Answered: Shahid Iqbal on 30 Jun 2019
syms n;
t = (-300:1:300);
D_n = ((sin((pi*n)/2))./(pi*n));
y = (D_n).*exp((-j)*n*t*(pi/100));
x = symsum(y,n,-10,-1) + symsum(y,n,1,10);
plot(t,x);
I would like to plot t vs. x, however I get the error 'Conversion to double from sym is not possible'.
  1 Comment
Christopher Creutzig
Christopher Creutzig on 17 Nov 2011
Works fine for me. Are you using exactly the commands listed above? Which MATLAB version are you using? What does symvar(x) tell you?

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Answers (2)

Walter Roberson
Walter Roberson on 14 Nov 2011
Your x is a formula in terms of n, a variable you do not define a value for at any point.
Your t value has nothing to do with n.
You cannot plot a symbolic expression against an unrelated variable.
Perhaps what you want is
plot(t, double(subs(x,n,t)))

Shahid Iqbal
Shahid Iqbal on 30 Jun 2019
syms n;
t = (-300:1:300);
D_n = ((sin((pi*n)/2))./(pi*n));
y = (D_n).*exp((-1i)*n*t*(pi/100));
x = symsum(y,n,-10,-1) + symsum(y,n,1,10);
plot(t,x);
work properly just replace -j with -1i , use updated version of MATLAB.

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