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ODE solution transfer

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111419] ODE solution transfer
  • From: EF <he.frauendorfer at t-online.de>
  • Date: Sat, 31 Jul 2010 02:42:57 -0400 (EDT)

  Moin,

  for the following sample ODE with the variables a[t] and b[t]

  deqns={a'[t]== -k*a[t], a[0]==2,
         b'[t]==  k*a[t], b[0]==0};
  k=0.08;
  start=0;end=10;

  the lists  vars  = {a[t],b[t]}
  and        fvars = {a[t_],b[t_]} are declared.

  Doing:

  {a[t_],b[t_]}=vars/.NDSolve[deqns,vars,{t,start,end}][[1]]
   gives the function values for a[t] and b[t], e.g. a[5] = 1.3406

  Using:

  fvars=vars/.NDSolve[deqns,vars,{t,start,end}][[1]]
  gives no function values for a[t] and b[t], entering a[5] returns
  no numeric value. fvars can be plotted however.

  The Full Forms of the corresponding expressions show no differences.
  I tried Thread, Map, Apply, Set @@@  etc without result.
  For ODEs with more than 100 variables, a form like fvars
  generated from vars would be useful.

  Please suggest a fix, Thanks

  E.F.



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