greg.smith <pg*****@hotmail.com> wrote:

I've been trying to solve this different via numerical methods(C

programming) and it's driving me crazy....
I can't post my code because it's simply one big mess and doesn't work.
d^2y/dx^2 - 1/(L^2)*y .... where L is just some arbitrary number......L =

0.2045....

That's not an equation, just a sum of two terms (or do you mean that's

the left hand side and the other side is 0), and your also not telling

about the boundary conditions or initial values for y and y' which you

will need for a numerical solution.

I cannot figure this out, I was thinking matlab might be easier but I really

want to learn to do this via the C language. I just want to solve for

values of Y, and plot them against x.

You don't show any code and you don't tell what method you try to use

(there are quite a number of methods of varying quality) so what kind

of help are you expecting? Have you been looking at "Numerical Recipes

in C" by Press et al.? While the code in the book is quite horrible,

chapter 16 and 17 give a useful introduction to numerically solving DEs

(and more information than you can expect from Usenet postings). You

can download the chapters from e.g.

http://www.library.cornell.edu/nr/bookcpdf.html.

Regards, Jens

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