I have produced a polynomial trend line in a graph. I now want to produce
that curve but the equation provided on the graph does not produce it. Is it
possible for Excel to produce that equation for me directly onto a sheet and
thus enable me reproduce the curve so that I can then use the values in a
look up table? Help?

If the equation doesn't seem to be producing the same as the trendline
you're seeing on the grpah, it's probably because you're not using enough
decimal places for your coefficients.
--
David Biddulph

"All at Sea" <All at wrote in message
...
I have produced a polynomial trend line in a graph. I now want to produce
that curve but the equation provided on the graph does not produce it. Is
it
possible for Excel to produce that equation for me directly onto a sheet
and
thus enable me reproduce the curve so that I can then use the values in a
look up table? Help?

All at Sea -

One way to get the coefficients on a worksheet is to use the array-entered
LINEST function (Control+Shift+Enter). For a polynomial of order 3, use

=LINEST(y-range, x-range^{1,2,3})

One of the reasons that your equation may seem incorrect is you may be using
a Line chart type (which defaults to 1,2,3,... for the x values) instead of
an XY (Scatter) chart type (which uses the numerical x values).

Another reason for differences is that you may not be displaying enough
significant digits.

- Mike Middleton
http://www.DecisionToolworks.com
Decision Analysis Add-ins for Excel



"All at Sea" <All at wrote in message
...
I have produced a polynomial trend line in a graph. I now want to produce
that curve but the equation provided on the graph does not produce it. Is
it
possible for Excel to produce that equation for me directly onto a sheet
and
thus enable me reproduce the curve so that I can then use the values in a
look up table? Help?