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MathGroup Archive 2005

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Re: function of a function

  • To: mathgroup at
  • Subject: [mg62628] Re: function of a function
  • From: "Jens-Peer Kuska" <kuska at>
  • Date: Tue, 29 Nov 2005 06:44:10 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <dmha20$932$>
  • Sender: owner-wri-mathgroup at


it can't work because f[0]==1 give in your 
differential equation
f'[0]==f[1] and NDSolve[] can't find the value for 
f[1] until it
has integrated the equation.
The neted dependence is equvalent to a infinite 
system of
ordinary differential equations and it seems to be 
hard to do
this by a finte computer.


"Narasimham" <mathma18 at> schrieb im 
Newsbeitrag news:dmha20$932$1 at
| Tried to solve numerically:
| thus:
| EQ= { f'[x] == f[f[x]], f[0]== 1} ; 
| But gives an error.  NDSolve::ndnum: 
Differential equation does not
| evaluate to a number at x = 0.
| Also does not work even with other f[0] values. 
Any way to do that?

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