combining three non linear functions into one single function.... I am performing one experiment in which I have a system output as Q which fundamentally depends on 3 independent inputs h,P,F. i.e. Q=G(h,P,F)....where G is some function. To quantify the dependence I varied h keeping P,F constant and got a variation in Q. Similarly I got another experimental plot of Q vs P where h,F are constant and also one Q vs F plot for constant h,P I did a curve fit in MATLAB cftool and obtained some non linear functions. The equations are of the following form Q=a1*ln(h)+b1.....P,F constant Q=a2*P^b2+c2....h,F are constant....^ denotes exponentiation. Q=a3*F^b3+c3....h,P are constant , ^ denotes exponentiation. a1,a2,a3,b1,b2,b3,c2,c3 are all known constants. what I want is to combine these three functions of h,P,F and obtain G such that Q=G(h,P,F) any help?