Excel 2007 - Can I add to a Line of Best Fit

[RFJ]

I've got a scattergraph and developed a line of best fit. (For info, it's a
4 order polynomial.)

What I'd like to do is show additional lines on the chart +/- 20% around the
calculated lobf - basically so I can see what points are outside that range.

Is there a way I can do it. Ideally a generic solution would be the best as
the next lobf could as easily be exponential.

TIA

Rob

 

[Del Cotter]

I've got a scattergraph and developed a line of best fit. (For info, it's a
4 order polynomial.)

What I'd like to do is show additional lines on the chart +/- 20% around the
calculated lobf - basically so I can see what points are outside that range.

You say you "developed" it. Was this actually in the spreadsheet cells,
or just using the trendline chart feature?

If the former, then create a range of cells that references the first
range and multiplies it by 1.2, and another range that does the same,
except multiplying by 0.8.

 

[Jerry W. Lewis]

You can get the polynomial coefficients with LINEST(), or directly calculate
points on the polynomial curve with TREND().

Jerry