Polynomial equations (how to forecast) | Dashboards & Charts | Excel Forum

Hi there Excel wizards,

I have this basic list showing figures from this FY. I've done a scattergram and the polynomial type (R2 = 1) is heads and shoulders above the rest. As our sales (construction industry) is very variable, other types of formulae (linear/growth) just don't fit.

Is there anyone who can provide a formula that will cover the below accurately so I can put forward a [reasonably] accurate forecast till June 2017?

This is what I ended up with after many hours of copying/playing/ pulling hair out, but I have no idea what I've actually produced (much too hard for this old kiwi brain!) nor how to use it going forward;

=(INDEX(LINEST(W48:W50,V48:V50^{1,2}),1))*V48^2+(INDEX(LINEST(W48:W50,V48:V50^{1,2}),1,2))*V48^1+(INDEX(LINEST(W48:W50,V48:V50^{1,2}),1,3))

Some help in taking me through it would be extremely appreciated!

Sales:

July 16     2,197,145

Aug 16    1,906,933

Sep 16     2,496,752

Oct 16     1,932,643

Nov 16     2,105,187

Dec 16    1,722,192

Kindest regards from New Zealand

Rusty