yhat = hougen(beta,x)
yhat = hougen(beta,x) returns the predicted values of the reaction rate, yhat, as a function of the vector of parameters, beta, and the matrix of data, X. beta must have 5 elements and X must have three columns.
hougen is a utility function for rsmdemo.
The model form is:
 Bates, D. M., and D. G. Watts. Nonlinear Regression Analysis and Its Applications. Hoboken, NJ: John Wiley & Sons, Inc., 1988.