Re: Integrating an InterpolatingFunction times another function

*To*: mathgroup at smc.vnet.net*Subject*: [mg126057] Re: Integrating an InterpolatingFunction times another function*From*: Yi Wang <tririverwangyi at gmail.com>*Date*: Sat, 14 Apr 2012 03:08:45 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jm8q6r$j74$1@smc.vnet.net>

Hi, Andrew, I guess Interpolation is more useful numerically. If you want a result, try NIntegrate[x*ifun[x], {x, 1, 5}] On the other hand, if you want an exact result: ifun2 = InterpolatingPolynomial[points, x] Integrate[x*ifun2, {x, 1, 5}] On Friday, April 13, 2012 5:04:27 AM UTC-4, Andrew DeYoung wrote: > Hi, > > I have made a sample InterpolatingFunction: > > points = {{0, 0}, {1, 1}, {2, 3}, {3, 4}, {4, 3}, {5, 0}}; > ifun = Interpolation[points] > > The following integral computes fine: > > Integrate[ifun[x], {x, 1, 5}] > > However, this integral will not be evaluated: > > Integrate[x*ifun[x], {x, 1, 5}] > > Why will this integral not be computed? Is there any way that I can > compute this integral? > > Thank you kindly! > > Andrew DeYoung > Carnegie Mellon University