Convert 3D Lookup Table

Hi,

I got a lookup table that looks like the following:

-Inf  40  50  60
0.70  22.70  9.24  6.78
0.65  20.45  8.85  6.42
0.60  19.23  8.48  6.69
0.55  18.04  8.03  6.28
0.50  16.89  7.63  6.49

Normally the inputs for the lookup table are:

X = 40 50 60 
Y = 0.70 0.65 0.60 0.55 0.5

And the other values is the interpolated output Z.

Now I want to convert the lookup table / this matrix so that

Y=Z .

This means, that I want the Z and the X Values as input and X as output.

How can I convert the matrix to get this ?

Thanks :)

[Walter Roberson]

Your notation

 Y=Z .

confuses me. You also said you want the Z and X as input and the X as output. Perhaps you want Z and X as input and Y as output? Y = Table(Z, X) ?

Answer 1

[Walter Roberson]

function Y = lookupY(X, Z)
XYZ = [-Inf 40    50  60
       0.70 22.70 9.24 6.78
       0.65 20.45 8.85 6.42
       0.60 19.23 8.48 6.69
       0.55 18.04 8.03 6.28
       0.50 16.89 7.63 6.49];

[numrow, numcol] = size(XYZ);
xcol = interp1(XYZ(1,2:end), 2:numcol, X, 'nearest', 'extrap');
yrow = interp1(XYZ(2:end, xcol), 2:numrow, Z, 'nearest', 'extrap');
Y = XYZ(yrow, 1);

[note: some errors have been corrected]