Re: weird interpolation issues

*To*: mathgroup at smc.vnet.net*Subject*: [mg96642] Re: weird interpolation issues*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Wed, 18 Feb 2009 04:23:05 -0500 (EST)

On 2/17/09 at 6:24 AM, okty.gy.ned at gmail.com (Ned Lieb) wrote: >I'm new to Mathematica and unfortunately am having some issues. I'm >trying to construct a program to create an approximate symbolic >function from a very large list of data points (6900 points, each >with five associated variables). Mathematica is fritzing in two >areas: first (this is probably trivial to fix), parallelization >doesn't initialize; second, the lists of variables I'm extracting >from my data table aren't being recognized as data points >Mathematica can interpolate between. I've copied the plaintext of my >source-code with comments explaining what each function is meant to >do below. >This is the Function I use to import my table. This seems to work >correctly: I get a list of numbers which matches my data >q[]=Import["C:\wfout2_k1_b1_s1_in.dat","FieldSeperators"->" >","LineSeperators"->"/[NewLine]" ,"RepeatedSeperators"->"True"] I very strongly suspect this is not doing what you think. I can think of no reason to create a function with no arguments and then define it to have a value equal to the data being read in. That is what you are doing with q[]. I am almost certain you would be better off using a simple variable, q, i.e. q = Import["C ... >This is a function I use to switch rows and columns, so that I have >five lists of values coresponsing to my variables instead of a list >of ~60000 points each carrying five values >w[q]:=Transpose[q]; You want to use w = Transpose[q] here. Note you could do this in one step by doing w = Transpose@Import["C: ... dispensing with any need for q. >This defines the last two variables as the real and complex values >of the function I'm trying to create by interpolation >wf[r_,c_]:=r+I*c; When using SetDelayed (:=) there is no need to terminate the definition with a ;. The whole point of SetDelayed is to delay evaluation. Consequently, there is no output returned when you don't terminate the definition with a ;. Of course, using a ; to terminate the definition causes no harm. It doesn't do anything in this case. >This is supposed to interpolate my imported values into a function >DistributeDefinitions[w,wf,\[Psi],q]; I would define all of the functions before making a call to DistributeDefinitions. The order you've done things may work. It isn't clear to me whether it will or not from the documentation. >\[Psi][x_,y_,z_,r_,c_]:=Interpolation[{x,y,z},Abs[wf[r,c]],{x,{w[[1] >]}},{y,{ w[[2]]}},{z,{w[[3]]}},{r,{w[[4]]}},{c,{w[[5]]}}]; It isn't clear to me what this function is supposed to do. I very much suspect you do not have it defined in a sensible manner. Looking below, I see you are using x,y and z to be scalars given values to be supplied by ContourPlot. That means the first argument to Interpolation is a list of 3 elements, the next is whatever is returned by wf, followed by arguments of the form {number, {{number, number .... }}}. This doesn't look like anything Interpolation is designed to accept. Look at the documentation for Interpolation. >This is supposed to make a graph of the function I made >above with the function's values being shown by contour density >ContourPlot3D[\[Psi],{x,0,20},{y,0,20},{z,0,20}] This will be returned unevaluated by Mathematica. At the very least this needs to be re-written as: ContourPlot3D[\[Psi][x,y,z,r,c],{x,0,20},{y,0,20},{z,0,20}] That is you need to call \[Psi] with the arguments you defined it to require. Note, the way I've rewritten things it still won't work since neither r nor c are defined.

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