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MathGroup Archive 2012

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Wrapping NDSolve within a function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg126337] Wrapping NDSolve within a function
  • From: bbeckage <Brian.Beckage at uvm.edu>
  • Date: Wed, 2 May 2012 05:44:45 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

When I try to return the interpolating function produced by NDSolve from 
within a function, the object returned has an unexpected $7360 appended, 
e.g.,

out = predState[1.5, 0.4, 0.2, 0.1, 0.0002, 0.0099]

(where predState is defined further below) results in

=
{{g$7360->InterpolatingFunction[{{0.,1000.}},<>],p$7360->InterpolatingFunction[{{0.,1000.}},<>],q$7360->InterpolatingFunction[{{0.,1000.}},<>]}}

Note the g$7360 rather than just g.  If NDSolve is not wrapped within 
the function, it returns a plain 'g', i.e., g->InterpolatingFunction.... 
 The appended $7360 makes it difficult to use the interpolating function 
as I can't reference it within other functions as the integer changes 
with each function call, e.g., g$7360[10] /. out, then g$7370[10] /. 
out, rather than being able to access it using the expected g[10]/.out.

Why  is this $7360 appended to g?  How can NDSolve be wrapped in a 
function, but be made to return a plain g?

Thanks for your help.

Best wishes,
Brian



predState[rg_, rp_, rh_, Mg_, Mp_, Mh_] :=
 Module[{parmList3woC, parmListND3woC, A, B, Rb, Rc, g, p, q, solND},
  parmListND3woC = {A -> Mg/rg, B -> Mp/rg, C -> Mh/rg, Rb -> rp/rg,
    Rc -> rh/rg};
  solND =
   NDSolve[{
     g'[t] == g[t]*(1 - g[t] - p[t] - q[t]) - A*g[t]*g[t] /. parmListND3woC,
     p'[t] == Rb*p[t]*(1 - p[t] - q[t]) - B*p[t]*g[t] /. parmListND3woC,
     q'[t] == Rc*q[t]*(1 - q[t]) - C*q[t]*g[t] /. parmListND3woC, g[0] == 0.5,
      p[0] == 0.5, q[0] == 0.5}, {g, p, q}, {t, 0, 1000}];
  Return[solND]
  ]










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