Conversion from double to sum not possible - Plot, please help!

Hello, here is my code:

_______

syms x;

syms theta;

y = exp(-abs(x/pi))

a0 = (1/pi)*int(y,0,pi);

dy = diff(y,1);

k = 1:10;

for i = 1:length(k)

      a(i) = ((-1)^(i))*2*dy/(i^2);
  end

for i = 1:length(k);

      g(i) = a(i)*cos(i*theta);
  end

fit = a0 + g;

theta = linspace(-pi,pi,50);
plot(theta,fit);

_____

However I get an error saying "Conversion from double to sym is not possible when I try to plot.

My "fit" equation works just fine., I get an equation in terms of 'theta'. But when I try to plot this equation vs, values of theta, these values are in an array, i get the error.

Can somebody please let me know what I should do, specifically, to fix this?

Thanks!!!!

Answer 1

[Matt J]

You cannot plot "equations". You can only plot points. You must evaluate your fit at the series of points that you would like to plot. Then plot those values.