Brian Dunning's FileMaker Custom Functions

interpolate ( x ; y ; t ; 0 ; 0 )

Polynomial interpolation of arbitrary degree

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Wilhelm Werner   Wilhelm Werner

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  Sample input:
interpolate("1¶2¶4¶8";"1¶2¶3¶4"; 3,24;0;0)
  Sample output:
2,739370666666666667

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Custom function implementation of Neville's algorithm for polynomial interpolation; see http://en.wikipedia.org/wiki/Neville's_algorithm .
The degree of the interpolating polynomial is determined by the length of the lists x resp. y; if ValueCount(x)=n then the degree is n-1.
The sample output above therefore is the value of the third degree interpolating polynomial at t=3,24.

 

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