File:Correlation examples.png

Summary

An example of the correlation of x and y for various distributions of (x,y) pairs. It was created by this Mathematica 6 code, which I wrote and release into the public domain (needs makePlot!):

n = 2000;
GraphicsArray[{
  Table[makePlot[
    Table[{RandomReal[NormalDistribution[0, 1]], (1 - Abs[w])*
        RandomReal[NormalDistribution[0, 1]]} . 
      RotationMatrix[-Sign[w]*Pi/4], {i, -1, 1, 2./n}], 1000], {w, 
    1, -1, -1/3}],
  Table[makePlot[Table[{x, slope*x}, {x, -1, 1, 2./n}], 100], {slope, 
    1, -1, -1/3}],
  {
   makePlot[
    Table[{x + RandomReal[]/3, 
      4 (x^2 - 1/2)^2 + RandomReal[]/500} , {x, -1, 1, 2./n}], 2000],
   makePlot[
    Table[{RandomReal[{-1, 1}], RandomReal[{-1, 1}]} . 
      RotationMatrix[-Pi/8], {x, -1, 1, 2./n}], 1400],
   makePlot[
    Table[{RandomReal[{-1, 1}], RandomReal[{-1, 1}]} . 
      RotationMatrix[-Pi/4], {x, -1, 1, 2./n}], 1400],
   makePlot[Table[{x, x^2 + RandomReal[]}/2, {x, -1, 1, 2./n}], 
    1400],
   makePlot[
    Table[{x, x^2 + RandomReal[]/2}*(RandomInteger[1]*2 - 1), {x, -1, 
      1, 2./n}], 1000],
   makePlot[
    Table[{Sin[x*Pi] + RandomReal[NormalDistribution[0, 1/8]], 
      Cos[x*Pi] + RandomReal[NormalDistribution[0, 1/8]]}, {x, -1, 1, 
      2./n}], 1400],
   makePlot[
    Table[{RandomReal[NormalDistribution[0, 1/3]], 
       RandomReal[
        NormalDistribution[0, 1/3]]} + {RandomInteger[1]*2 - 1, 
       RandomInteger[1]*2 - 1}, {x, -1, 1, 2./n}], 1400]
   }
  }]

Licensing

This work has been released into the public domain by its author, Imagecreator at the wikipedia project. This applies worldwide. In case this is not legally possible: Imagecreator grants anyone the right to use this work for any purpose, without any conditions, unless such conditions are required by law.

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