Error: Too many functions when plotting series

x=[0:pi/100:2*pi];
figure;
syms k;
syms f(x);
S1 = symsum((1/k)*sin(k*x),k,1,Inf); 
S2 = symsum((1/(2*k-1))*sin((2*k-1)*x),k,1,Inf); 
fplot(x,S1,x,S2);

Error using fplot
Too many functions.

xlabel('x')
ylabel('y')

I get this error when I'm trying to plot two series, what did I do wrong?

And how to properly apply the domain from 0 to 2pi ?

Answer 1

[Walter Roberson]

x=[0:pi/100:2*pi];

That creates a numeric x in steps of

syms f(x);

That is equivalent to

syms x
f = symfun('f(x)', x)

which has the side effect of overwriting x with a symbolic variable.

fplot(x,S1,x,S2);

fplot does not accept x, y pairs at all. If you want to plot multiple functions, put the functions into a vector, as the first parameter. The second parameter, if provided, must be the lower and upper bound to plot over.

fplot([S1, S2], [lower_bound, upper_bound])

Note that at this point, x is the symbolic x, since you overwrote the numeric x with symbolic x.

You should be using

xrange = [0, 2*pi];
syms k;
syms f(x);
S1 = symsum((1/k)*sin(k*x),k,1,Inf); 
S2 = symsum((1/(2*k-1))*sin((2*k-1)*x),k,1,Inf); 
fplot([S1,S2], xrange);
xlabel('x')
ylabel('y')

OR you can subs() particular numeric x values into S1 and S2 and use plot()

Answer 2

[Rik]

I suspect this will do what you want:

fplot(x,S1);
hold on
fplot(x,S2) 
hold off