how do I get an interpolated scalar value from a 2D lookup table z=f(x,y)?

[Hoard]

I have a table of numerical values.  Rows correspond to discrete values of a parameter, columns to discrete values of a second parameter.  I want tin interpolate a scalar value from the table :

Table Z = f(X,Y)

find Zi,j corresponding to specified X and Y values (which may not be the exact discrete valuescorresponding to rows and columns).

So, I want to find Z(1.5, 3) from a table

    X    1      2     3

Y

2       10   15    20

4        50   60   70

The results would be Z = 33.75

The LUT routines interpolate an entire table rather than giving a single answer.  earlier discussions have posted routines that find the nearest table entry but do not interpolate between entries.

This sounds very simple....

Thanks.

[altenbach]

Have a look at the bilinear interpolation examples quoted in the various links of this idea.

(Use threshold array to get the fractional array index from the axis mapping)

[Hoard]

Thanks!  The function is exactly what I was looking for.