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MathGroup Archive 2005

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surface fitting question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61328] surface fitting question
  • From: Ralph Smith <ralph at lkjlkj.com>
  • Date: Fri, 14 Oct 2005 22:23:55 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I have this data in a file. It is a 2D table that 26 rows and  17 columns.

     |
-----------------------------------------------------------------------
     |   0.000    0.000   0.000   ...     0.000     0.000     0.000
     |   0.050    0.050   0.155   ...    16.409    19.375    20.156
     |                       .
     |                       .
     |                       .
     |  47.500  50.000  55.000   ...   2017.500  2075.580  2182.765
-----------------------------------------------------------------------
     |

I would like to find an equation that describes this surface using
mathematica. I think that 3rd degree polynomials would be what I'm looking
for. So, maybe
   data[x,y] = ax^3 + bx^2 + cx + d + ey^3 + fy^2 + gy

I've seen and example that uses Fit[], so I think this can be done, but I'm
a novice at mathematica and don't know how to set this problem up. I have been
able to fit a polynomial to curve data, but now I need to fit a surface.

thanks,
Ralph




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