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

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!




TideMan <mulgor@gmail.com> wrote in message <b502bbbc-97af-4f99-a607-fbc80e972885@googlegroups.com>...
> On Tuesday, February 19, 2013 2:37:06 PM UTC+13, laura wrote:
> > 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!
>
> Here's what you need to get you started:
> help input
>
> Now, you write some code and when you get stuck come back here and ask for help.
> But don't expect us to do your homework for you.