Some methods of approximating discrete functions of several variables were investigated. The principal goal was a suitable approximation for aerodynamic and infrared signature data for use in real time hybrid computer simulations. The main thrust is toward approximation by sums of functions of fewer variables. Two computer programs are given, and a number of comparisons between three types of approximations are given. It is decided that no method for determining, a priori, the kind of approximation which will yield suitable results is known, except in special cases. (Author)