Adding and Integrating Interpolation Functions

[Bayers, Alexander]

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]

Use NIntegrate, not Integrate.

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

Bobby

--
DrMaj...@yahoo.com

[oshaughn]

> 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 = Integrate[#, {t, 2, 3}] & /@ (firstinterp[t] + secondinterp
[t])

creates a symbolic result.