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Re: Problems integrating InterpolatingFunction

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  • Subject: [mg116050] Re: Problems integrating InterpolatingFunction
  • From: Gary Wardall <gwardall at>
  • Date: Sun, 30 Jan 2011 03:32:47 -0500 (EST)
  • References: <ii2c82$ra6$>

On Jan 29, 6:43 pm, Sergio Miguel Terrazas Porras <sterr... at>
> Hello group,
> I use NDSolve for a nonlinear differential equation, and I get an InterpolatingFunction, as expected.
> I can plot it, evaluate it, etc.
> The problem I have is that now I need to integrate 1/(the square of the InterpolatingFunction), and I get nothing but the input back.
> Any ideas?
> Thanks in advance.
> Sergio Terrazas

I'm a bit rusty with my ODE theory but you might try restating your
problem in terms of a system of ODE's.


y1=92=f(x)      &   f(x0)=y10       (The function you used with NDSolve
on originally.)


y2=Integral( 1/(f(x)^2 )         (The function you really want at the



Then the system to solve would be:

y1=92=f(x)               &    y1(x0)=y10

y2=92=1/(y1)^2      &     y2(x0)=0

I hope this or a some variation should be of some help.

Gary Wardall

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