Polynomial fitting with multiple variables and unequal matrix length

Hi, Good day. Thanks in advance. I'm having problem with investigating relationship with some data. Say, A=1,2,3.. and for each A, there are 20 values of B and C correspond to B (I mean C depends on B). I can easily find a polynomial relationship between B and C but how can I create relationship between A, B and C? Please note that, I'm actually a new in Matlab, thus don't take it otherwise if the question seems somehow not appropriate.

In simple:

A=[1 2 3 4 5].

For A=1, B=[... ... ... 20 values] and C=[... ... ... 20 values]

For A=2, B=[... ... ... 20 values] and C=[... ... ... 20 values]

....

For A=5, B=[... ... ... 20 values] and C=[... ... ... 20 values].

Need to have a relationship between A, B and C.

Thanks again.

Answer 1

[Iain]

It kinda depeneds how those variables interact.

A "simple" method is to use the polyfit function to get a suitable relationship, for each value of A, for B to relate to C. (Quadratic/cubic/whatever).

So you get, for A = 1, C = d + eB + fB^2-hB^4 (or whatever)

Then you have 5 "A" values, 5 d values, on which you can do the same again...

To get something like d = A/4 + 0.1; e = A^2/20

[Md Jahirul Islam]

Thank you very much Iain. It's helpful but could you please explain the last part a little more? Finally say, I've

A=[1

2

...

5] and

C=[ d1 + e1B + f1B^2 . .

d2 + e2B + f2B^2 . .

..

d5 + e5B + f5B^2 . .].

How can I get the relationship?

Thanks again.