Re: NDSolve error message: Can't find starting value ...
- To: mathgroup at smc.vnet.net
- Subject: [mg23798] Re: NDSolve error message: Can't find starting value ...
- From: "Bill Bertram" <wkb at ansto.gov.au>
- Date: Sat, 10 Jun 2000 02:59:53 -0400 (EDT)
- Organization: Australian Nuclear Science and Technology Organisation
- References: <8hfggl$i4h@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Axel Kowald <axel at itb.biologie.hu-berlin.de> wrote in message news:8hfggl$i4h at smc.vnet.net... > 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 ? Axel, For this case Mathematica requires boundary conditions in terms of R and R'. Your boundary conditions on R'' should be recast using the DE. Presumably they would be R[-3] == 0 and R[3] == 0. Mathematica is then quite happy but I don't know if you'll be, because the solution it gives is R[x] =0 for all x. Cheers, Bill