Theta function - Wikipedia
https://en.wikipedia.org/wiki/Theta_functionIn mathematics, theta functions are special functions of several complex variables. They are important in many areas, including the theories of Abelian varieties and moduli spaces, and of quadratic forms. They have also been applied to soliton theory. When generalized to a Grassmann algebra, they also appear in quantum field theory.
Matlab - theta
mooring.ucsd.edu › software › matlabMay 09, 2009 · THETA Computes local potential temperature at reference pressure. PTEMP = THETA(P,T,S,P0) is the local potential temperature at reference pressure P0 using Bryden 1973 polynomial for adiabatic lapse rate and Runge-Kutta fourth order integration algorithm.