Re: InterpolatingPolynomial error message

*To*: mathgroup at smc.vnet.net*Subject*: [mg115733] Re: InterpolatingPolynomial error message*From*: Barrie Stokes <Barrie.Stokes at newcastle.edu.au>*Date*: Wed, 19 Jan 2011 05:28:56 -0500 (EST)

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