graph to equation

Hi

I have found out the impedance graph of monopole antenna on two plates(plates r 90 deg) by moving it frm center towards edge by a simulation software..I need to write a equation for that graph so that i can use this equation to get impedance graph without simulating for different plate dimension..

I don no how to strat this ? is their any procedure to do it?r i need to for error n trial method..PLZ help me..

In order words :

You have got a graph which you need to find a best fit equation for it ?

Maybe you can use Matlab for it.

Yes you can use the curve fitting. There are alot of curve fitting methods.

you can use curve fitting functions in MATLAB.
Simple guide for curve fitting is attached.