Re: Function Fit to 3D data set

*To*: mathgroup at smc.vnet.net*Subject*: [mg57758] Re: Function Fit to 3D data set*From*: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>*Date*: Tue, 7 Jun 2005 05:59:47 -0400 (EDT)*Organization*: Uni Leipzig*References*: <d83eh8$o6e$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, a) use TriangularSufacePlot[] from <<DiscreteMath`ComputationalGeometry` TriangularSurfacePlot[data3D] b) points = {{1, 1, 1}, {1, 2, 4}, {1, 4, 16}} f1 = FindFit[points, a + b*x^0 * y^1 + c*x^0 *y^2 + k*x^2 *y^0 + l*x^2 * y^1, {a, b, c, k, l}, { x, y}] work as expected. Regards Jens "Adrienne R" <roehrich at unlserve.unl.edu> schrieb im Newsbeitrag news:d83eh8$o6e$1 at smc.vnet.net... >I have been trying to do several analyses with an >[x,y,z] data set, where z is dependent on x and >y. First, I tried a 3D plot. However, the only >way I was able to get Mathematica to plot my data >was to assume a grid form for x and y, and use >ListPlot3D. First question: can Mathematica make >a 3D plot from stated x,y,z points? > > Secondly, I am trying to fit a function to the > data. I have determined a function to which to > fit parameters. However, Mathematica does not > seem to want to accept y as a variable. Here is > a simple suggestion of what I was trying. Note, > my function is much more complicated. Please > also ignore if the given does not work as > stated, as I'm making it up. > > points = {{1, 1, 1}, {1, 2, 4}, {1, 4, 16}} > f1 = FindFit[points, a + b*x^0 * y^1 + c*x^0 > *y^2 +k*x^2 *y^0 + l*x^2 * y^1, {a, b, c, k, l}, > x, y] > > The error I receive is \!\(\* > RowBox[{\(FindFit::"nonopt > "\), \(\(:\)\(\ \)\), "\<\"Options expected ( > instead of \\!\\(y\\)) beyond > position \\!\\(4\\) in > \\!\\(\[LeftSkeleton] 1 \[RightSkeleton]\\). An > \ > option must be a rule or a list of rules. > \\!\\(\\*ButtonBox[\\\"Moreâ?¦\\\", \ > ButtonStyle->\\\"RefGuideLinkText\\\", > ButtonFrame->None, \ > ButtonData:>\\\"General::nonopt\\\"]\\)\"\>"}]\) > > Second question: Can Mathematica take a set of > x,y,z data where z is dependent on x and y and > fit a function to it? > > Secondary question for both: How? > > Thanks for the help! >