# TLOOKUP

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## Contents

#### TLOOKUP - table lookup, interpolation

##### Usage:

`TLOOKUP X XP YP TYPE INV`

##### Inputs:
 X argument (number or vector) XP vector of X-values YP vector of Y-values: YP[i] = f(XP[i]) TYPE type of interpolation INV selects how to process invalid X-values
##### Outputs:
 Y interpolated function values (same type as X)
##### Function:

For each X-value, an interpolated Y-value for the function defined by the value pairs (XP[i], YP[i]) is computed. All inputs except TYPE and INV are updated at the beginning of each evaluation cycle.

Interpolation method selected by input TYPE{| |- |value of TYPE |interpolation method |- |0 or SPLINE |spline interpolation, not yet implemented |- |1 or LINEAR |linear interpolation between two points of the function |- |2 or NEVILLE |polynomial interpolation using the Neville algorithm |- |3 or NEWTON |polynomial interpolation using the Newton algorithm |}

Processing of invalid X-Values (values outside the range min(XP)..max(XP)){| |- |value of INV |interpolation method |- |0 or EXTRAPOLATE |the value of Y is extrapolated, cannot be used with TYPE=LINEAR |- |1 or TRUNCATE |the X-value is "forced to be valid" |- |2 or LEAVE |no interpolation, Y is set to X |}