Re: NDSolve error message: Can't find starting value ...
- To: mathgroup at smc.vnet.net
- Subject: [mg23786] Re: NDSolve error message: Can't find starting value ...
- From: "Kevin J. McCann" <kevin.mccann at jhuapl.edu>
- Date: Sat, 10 Jun 2000 02:59:31 -0400 (EDT)
- Organization: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
- References: <8hfggl$i4h@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Axel, A coulple of things. First off you need to specify R[x] and R'[x] at some point in the interval to get things moving. Second, I am not sure that a numerical integration will treat the delta function correctly. You might consider finding solutions on either side to of x=0 and finding the constants by integrating over an infinitesimal interval around x=0. In fact, you are solving for the Green's function of the DE. Kevin Axel Kowald <axel at itb.biologie.hu-berlin.de> wrote in message news:8hfggl$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 ? > > Many thanks, > > Axel Kowald > > P.S. Btw., this is done with Mathematica 4. > > >