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lagrange interpolation and derivative

by Geoff Wawrzyniak

14 Aug 2006 (Updated 24 Aug 2006)

No BSD License

This function performs the Lagrange interpolation of a function and its derivative.

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Description

This function performs the Lagrange interpolation of a function (y) or its derivative (dy/dx).

usage:
y=lagrange(x,pointx,pointsy,0) or
dy=lagrange(x,pointx,pointsy,1) or
dy=lagrange(x,pointx,pointsy,2)

There are two ways to find the derivative. If dydx_on (varargin(4)) is set to 1, it will base the derivative on pointx and pointsy (y will be dy/dx). If dydx_on == 2, the derivative is based on the interpolated points.

pointsy can be an array.

This function can get slow for large amounts of control points. Also, make sure to have extra control points outside the region of interpolation interest if there are lots of control points.

Acknowledgements

The author wishes to acknowledge the following in the creation of this submission:
Lagrange polynomial interpolation
This submission has inspired the following:
Lagrange Interpolator Polynomial

MATLAB release

MATLAB 7.0.4 (R14SP2)

Tags for This File
Everyone's Tags	approximation, derivative, differential, interpolation, lagrange
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Comments and Ratings (1)
09 Aug 2008	dudu zama

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Updates
24 Aug 2006	Found error in the description of input arguments. Polished up code per the code metrics.

Tag Activity for this File
Tag	Applied By	Date/Time
approximation	Geoff Wawrzyniak	22 Oct 2008 08:34:59
interpolation	Geoff Wawrzyniak	22 Oct 2008 08:34:59
lagrange	Geoff Wawrzyniak	22 Oct 2008 08:34:59
derivative	Geoff Wawrzyniak	22 Oct 2008 08:34:59
differential	Geoff Wawrzyniak	22 Oct 2008 08:34:59

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