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The y-value at which to interpolatey

The x-value at which to interpolatex

3x3 matrix of the table z-valueszmat

Three-element list of the table y-coordinates {y1,y2,y3}yl

Three-element list of the table x-coordinates {x1,x2,x3}xl

The z-values are passed as a 3x3 matrix only because that is a convenient way for the user to enter

the z-values, directly as they appear in a printed table.

The first two when() functions scale x and y to u and v as shown in [7]. The last line of the function

calculates and returns the interpolation result. The augment(augment(...))

convertst the 3x3 z-matrix

to a single-column vector, to perform the matrix multiplication in [10]. The coefficient solution vector is

converted to a list, so that the built-in list multiplication can be used to find each term of the sum in [11].

As an example, suppose that we want to interpolate with this table at x = 0.27 and y = 0.55:

0.43500.33350.24740.3

0.38940.28600.19870.2

0.36160.25710.16920.1

0.60.50.4

So we have

xl = {.1, .2, .3}

yl = {.4, .5, .6}

zmat =

.1692 .2571 .3616

.1987 .2860 .3894

.2474 .3335 .4350

x = 0.27

y = 0.55

and the call to do the interpolation looks like

intrpz9({.1,.2,.3},{.4,.5,.6},[.1692,.2571,.3616;.1987,.286,.3894;.2474,.3335,

.435],0.27,0.55)

which returns 0.3664.

This program, intrp9ui(), provides a user interface for intrpz9().

intrp9ui()

Prgm

local x123,y123,zz1,zz2,zz3,xy,res,xl,yl,zmat,x,y,z,inhome,errdisp

define errdisp(msg)=Prgm

dialog

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Texas Instruments TI-92+ User Manual

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