formula from curves for two inputs

**dear all, **

**Hello,**

**I need your help in this matter,**

**the discription of the subject is:**

**we have two input vectors ( included in one vector):**

**T ( temperature ) and H ( humidity ), there is a corresponding one output**

**P ( power demand ), and all these data are normalized**

**I have thousands of data for these values done for many years.**

**for sample example: ( l assume that we have the data for 5 hours )**

**T_H=[0.3333 0.3333 0.3542 0.3750 0.3750 ; 0.6970 0.8384 0.6869 0.7980 0.7677]**

**and the corresponding P is:**

**P=[0.6561 0.6618 0.6568 0.6694 0.6622]**

**I need to draw a curves relating all data,**

**and THE MOST IMPORTANT THING WHICH IS THE AIM OF MY PROBLEM IS :**

**finding ( inventing ) a formula depending on the curves drawn that relates**

**the power as an output with the temperature & humidity as inputs,**

**meaning:**

**P = f (T,H)**

**for example: the formula model may be:**

**P = a0 + a1 * T + a2*H*sin(T) + a3*T^3*H + a4*T*H **

**then finding a0,a1,a2 and a3 and this is easy and I**

**know how to find them.**

**BUT, my problem is how can I find this above example model function P ?**

**is it by dividing the curve to parts and then finding a function**

**for each part ? but how is this done by MATLAB ?**

**Any idea ?**

**Can anybody help me? I am appreciating any help.**

**and remember, any service will be valuable for me**

**Best regards **