LOOKUP and Filter Based on Combined Condition

The first thing I did was to copy paste the formula back down the sheet. I modified the formula in G:

=IF(A2="","",C2/31000)

I then set up two Named Ranges (CTRL-F3 to view edit) - Rad and AC_Pwr looking like this:

='Filter Data'!$G$2:INDEX('Filter Data'!$G$2:$G$130,SUMPRODUCT(--(LEN('Filter Data'!$G$2:$G$130)>0)))

I then went to Chart tools/design/select data/Linear regression/Edit

and changed the references to the X and Y data like this:

='Test sheet (2) (1).xlsx'!Rad

It's ESSENTIAL to include the filename!! OK/OK.

That's it, I think... Now you can change some )s to 1s on the raw data and the regression remains correct