Error: Too many functions when plotting series
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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);
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 ?
采纳的回答
Walter Roberson
2022-12-4
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()
更多回答（1 个）
Rik
2022-12-4
I suspect this will do what you want:
fplot(x,S1);
hold on
fplot(x,S2)
hold off
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