Re: NDSolve error message: Can't find starting value ...
- To: mathgroup at smc.vnet.net
- Subject: [mg23768] Re: NDSolve error message: Can't find starting value ...
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Sat, 10 Jun 2000 02:59:14 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <8hfggl$i4h@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
for a second order equation you have to supply the
function value R[x] *and* the first dervative R'[x],
or R[x1] and R[x2] ...
but never a second derivatives like R''[-3].
NDSolve[] will not able to solve a equation with a
DiracDelta[] function because the numerical methods
require Lipschitz continuous right hand sides.
You should have a look in some undergraduate mathematics
books *before* you use Mathematica.
Regards
Jens
Axel Kowald wrote:
>
> Hello,
>
> I try to solve the following second order ODE with NDSolve
>
> NDSolve[{0 == R''[x] + DiracDelta[x] - R[x], R''[-3] == 0,
> R''[3] == 0}, R, {x, -3, 3}]
>
> and I get the following error message:
>
> NDSolve::"ndsv": "Cannot find starting value for the variable x."
>
> I couldn't find any description of this message in the Mathematica book, so I'm
> not sure what to do. I have a second order ODE with two boundary
> conditions, what's missing ?
>
> Many thanks,
>
> Axel Kowald
>
> P.S. Btw., this is done with Mathematica 4.