Re: help with writing a short program using square waves, fourier series expansion

okay so so far i got this


x=linspace(0,2*L,500);
y=4/pi;
maxn=500;
for n=0:(2*L)/(500-1):2*L;
    y=(4/pi)*(1/n)*sin(n*pi*x/L);
end
if L<=0
    error('L must be a positive integer');
end
if n~=n
    error('n must be an integer');
end
if ~mod(x,2)
    error('n must be odd');
end
plot(x,y)


but i know its wrong because my professor showed us how the graph is supposed to look like and im not getting that :/ Do you know where I messed up? Or any advice at all? thanks!


"laura " <lola_angelgirl@hotmail.com> wrote in message <kful02$qdn$1@newscl01ah.mathworks.com>...
> A square wave of period 2L is a step function which is equal to 1 for x from 0 to L, then is equal to -1 for x from L to 2L.
>
> A square wave can be approximated by this Fourier Series expansion:
> infinity
> f(x )=(4/pi) ?((1/n)sin(npix/L))
> n=1,2,3,5....
> I need to write a program that prompts the user for a maximum value for n and a value for L. Using those values, I have to compute the Fourier Series expansion for a square wave and plot the result.
> L must be a positive number, and n must be a positive odd integer. If the user does not provide an acceptable number, you should detect the error, display an error message, and stop your script.
> You should evaluate the function for 500 values of x, evenly distributed from 0 to 2L.
>
> I know this is alot but I have no idea how to even start it! If you can at least start me off that would be great!
> I know i need to get an input, detect an error, stop the script, and evenly distrubute 500 points im just not sure how. thanks again!