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How to interpolate big data with small deviation?

  1. May 25, 2013 #1
    Hi,
    I've got a problem. There is over 9 milions points in my .txt. I have to find polynom for surface of this points with deviation smaller then 0.01 (x [-3:3], y[-3,3], z [-9,9]).
    I try many functions in Matlab, but no answer.
    Thank for help.
    B
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 25, 2013 #2

    mfb

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    Staff: Mentor

    Which functions did you try in Matlab? Did you used a fit to determine the prefactors in your polynomials?
    Did you consider terms like x*y, x^2*y^4*z and similar? They might be required to approximate your data with a polynomial.
     
    Last edited: May 25, 2013
  4. May 25, 2013 #3
    Hi,
    main wasthis:
    m=[0 0 ; 1 0 ;0 1;2 0;2 1; 2 2 ;0 2;1 2; 3 0; 3 1;3 2; 3 3; 0 3;1 3; 2 3];
    coeff=least_square_polyfit_xyz(x,y,z,m);
    m are combinations of using x and y () so it will make a + b*x + c*y +d*x^2....
    bud there are very big diferences between defined z and computed z. The proble is, that my surface is only little curved plane, but there are 2 singularities (ist surface with volcanos).
     
  5. May 25, 2013 #4

    mfb

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    Ah, it is just f(x,y)=z
    Do you have to use a polynomial?

    11 is missing in your list.

    Is there any visible symmetry?
    What about terms of 4th order?
     
  6. May 25, 2013 #5
    I repair script, but there is no improve.
    This is the source of data, if you can try it. There is no symetry, so I don't know how to do this.
    http://m37.fsv.cvut.cz/nm/data.txt
    I've tried also 4th order, but also no improve.
     
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