Re: Adding and Integrating Interpolation Functions

• To: mathgroup at smc.vnet.net
• Subject: [mg103839] Re: [mg103801] Adding and Integrating Interpolation Functions
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Thu, 8 Oct 2009 07:53:03 -0400 (EDT)
• References: <200910071100.HAA00332@smc.vnet.net>

```Use NIntegrate, not Integrate.

(I can only guess you're using Integrate, since you didn't send the code.)

Bobby

On Wed, 07 Oct 2009 06:00:46 -0500, Bayers, Alexander
<alexander.bayers at baml.com> wrote:

> I have two interpolation functions, firstinterp and secondinterp, that I
> wish to add.  They are defined symbolically, i.e.
>
>
> a = {1, 2, 3, 4, 5}
>
> b = {b1, b2, b3, b4, b5}
>
> c = {c1, c2, c3, c4, c5}
>
>
> firstinterp = Interpolation[Transpose[{a, b}], InterpolationOrder -> 1]
>
> secondinterp = Interpolation[Transpose[{a, b}], InterpolationOrder -> 1]
>
>
> newinterp[t_]:= firstinterp[t] + secondinterp[t]
>
>
> While I can evaluate newinterp at any point, and I am able to integrate
> firstinterp[t] and secondinterp[t], when I run Integrate[newinterp[t],
> {t, 2, 3}] I receive (InterpolatingFunction[{{1, 5}}, <>][t] +
> InterpolatingFunction[{{1, 5}}, <>][t]) dt under an integral sign,
> rather than the evaluated value.  Does anyone know how to get this to
> integrate to its real value?
>
>
> Thanks,
>
> Alex
>
>
>

--
DrMajorBob at yahoo.com

```

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