Homework Help: Formula from curves for two inputs

1. Jun 18, 2010

MOOON

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

2. Jun 18, 2010

LCKurtz

You might Google quadratic Shepard's method and see if what you find there is a help to you. You might even find already done implementations.

3. Jun 21, 2010

MOOON

I think that the problem is mathmatics and

also it is related to numerical methods..

If we forget about electrical point of view and consider

the variables as three variables, one dependent ( P )

and the others are independent ( T & H )

How can we relate them in equation of the form: P = f ( T , H )

and the behaviour of the graphs and plots are nonlinear

knowing thousands of data of these variables ..

regards