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Re: InterpolatingPolynomial error message

  • To: mathgroup at smc.vnet.net
  • Subject: [mg129535] Re: InterpolatingPolynomial error message
  • From: wangkang0118 at gmail.com
  • Date: Mon, 21 Jan 2013 00:08:42 -0500 (EST)
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  • References: <ih6ecs$3f8$1@smc.vnet.net>

> Hi Victor
>
> 1. The form of your data is not right for InterpolatingPolynomial (see the online documentation).
>
> With
>
> data2 = {{{105, 1.5}, 33.0127}, {{110, 1.5}, 32.2962}, {{115, 1.5},
>    31.6448}, {{120, 1.5}, 31.054}, {{125, 1.5},
>    30.5196}, {{130, 1.5}, 30.0374}, {{135, 1.5},
>    29.6036}, {{140, 1.5}, 29.2143}}
>
> the command would then be
>
> InterpolatingPolynomial[data2, {x, y}]
>
> to get an interpolating surface in 3D. (I am assuming that is what " i am trying to get a function" means.)
>
> This input however gives the message
>
> InterpolatingPolynomial::poised: "The interpolation points {{105,1.5},{110,1.5},{115,1.5},{120,1.5},{125,1.5},{130,1.5},{135,1.5},{140,1.5}} are not poised, so an interpolating polynomial of total degree 3 could not be found"
>
> If you then do
>
> data3 = First /@ data2
>
> to get the {x,y} coordinates, and then do
>
> ListPlot[ data3 ]
>
> You'll see what is retrospectively obvious, that your original 3D points project onto a straight line on the (x,y) plane. (That's what the "not poised" message means.) How do you imagine Mathematica could construct an interpolating *surface* from this data?
>
> Cheers
>
> Barrie
>
> >>> On 18/01/2011 at 9:52 pm, in message <201101181052.FAA11815 at smc.vnet.  net>,
> VICTOR <victor.herasme at gmail.com> wrote:
> > Hi,
> >
> > i am trying to get a function for this data set:
> >
> > data={{105,1.5,33.0127},{110,1.5,32.2962},{115,1.5,31.6448},{120,1.5,31.054}
> > ,{125,1.5,30.5196},{130,1.5,30.0374},{135,1.5,29.6036},{140,1.5,29.2143},...}
> >
> > i execute the command:
> >
> > P=InterpolatingPolynomial[data,{x,y,z}]; And i get this error message:
> >
> > InterpolatingPolynomial::ipab: Abscissa specification 105 in
> > {105,1.5,33.0127} is not a point in 3 dimensions. >>
> >
> > I dond't know what's going on. Can anyone help me please ? Regards,
> >
> > Victor
Hi,
I am trying to solve this problem by mathematica. Write a program to interpolate the function f(x,y) = cos(x) sin(y) at 16 equally-spaced points in the square (-pi,pi) x (-pi,pi), using multi-dimensional polynomials that are cubics in each coordinate. Plot the error in the function value.
However, I tried a lot but still failed.
I was wondering if you could help me.
I sent you the attached material.
Thank you so much.
Kang




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