Create a equation

[eastorca]

Dear all,

I have a graph on PFD file. How can I change this to digital equation ( f(x) = a*x + b*x2.....) for easier look up by Excell. Which software build this one?

Thank you so much

[alexanderchacin]

Tried Microsoft Office Equation Editor, in excel 2003 and bellow is in inser object dialog from menu insert, in excel 2007 and after is in insert ribbon