Hey need assistance with fourier analysis questions

function [x,f]=my_Fourier_series_generator(T,a0,an,bn,xrange,max_N)

x=linspace(xrange(1),xrange(2),1000);

% frequency wn
w=2*pi/T;

% initializing f at a0
f=a0;

syms n;

% Fourier series implementation
for n=1:max_N
    aa=eval(an);
    bb=eval(bn);
    f=f+aa*cos(w*n*x)+bb*sin(w*n*x);
end
plot(x,f)

this is the code im trying to run

solution(1, 1/2, (2/(n*pi))*sin((n*pi)/2), 0, 0:10:200, 300)

this is the error I keep receiving

Error using eval

Must be a string scalar or character vector.

Error in solution (line 17)

bb=eval(bn);

Answer 1

[Walter Roberson]

You are passing (2/(n*pi))*sin((n*pi)/2) in the position you call an . You ask to eval(an), so you are asking to eval((2/(n*pi))*sin((n*pi)/2)) . However, eval() can only work on string objects or character vectors.

The likelihood that you are using eval() appropriately is... rather low. You should probably be passing in function handles and evaluating the function handles. Like

   aa = an(n)

after you have passed in

@(n) (2/(n*pi))*sin((n*pi)/2)

in that position.

[Christopher Carey]

Hi, Firstly thank you very much for your assistance i tried this but now i'm getting a different error

Index exceeds matrix dimensions.

Error in gui212>my_Fourier_series_generator (line 244)

      an2=an(n);

Error in gui212>Run_Callback (line 226)

[x,f]=my_Fourier_series_generator(T0,a0,an,bn,xrange,max_N)

Error in gui_mainfcn (line 95)
        feval(varargin{:});

Error in gui212 (line 42)
    gui_mainfcn(gui_State, varargin{:});

Error in

matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)gui212('Run_Callback',hObject,eventdata,guidata(hObject)) 

Error while evaluating UIControl Callback.

[Walter Roberson]

I said,

"after you have passed in @(n) (2/(n*pi))*sin((n*pi)/2) in that position".

You have not passed a function handle in that position: you have passed a scalar or vector of values.