I do agree that information is missing for more complex patterns but had a feeling that for less complex patterns and specific antenna configurations there might exist maybe an emperical approach to approximate the patterns to a reasonable extend.
Simulation would be the better option if the...
Have a look at:
IEEE Antennnas and propagation magazine vol43 no2 April 2001
for an article by Lius M Correia, Francisco Gil et al.
This is a good start but is still a linear interpolation process.
Pavlos
