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Re: Problems integrating InterpolatingFunction


On Sun, 30 Jan 2011, Sergio Miguel Terrazas Porras wrote:

> 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
>
>

Sergio,

here is an example

s = NDSolve[{y'[x] == y[x] Cos[x + y[x]], y[0] == 1}, y, {x, 0, 30}]
Plot[Evaluate[y[x] /. s], {x, 0, 30}, PlotRange -> All]

if = Evaluate[y[x] /. s][[1]]

NIntegrate[if, {x, 0, 30}]

Hope this helps,

Oliver


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