Hi Suzy,
I was working on a similar problem, but it did not have to do with a volume
problem, as much as it had to do with a 6th degree polynomial. It appeared
that the precision of 15 decimals places would not allow finding the "data"
points well enough. So I would like to see how this goes for you.

Assuming your data has not exceeded the 65000 row limit inherant in Excel,
there sould not be a reason a formula can not be copied either up or down,
depending your data layout. I believe the formula will have to be
"anchoraged" at either the top or bottom of your data range. I am not certain
that the formula yields specific "new" data points, which allow you to graph
the trend line, with out using the built in trend line in Excel, which is
what I was attempting to accomplish.

I had attemted to go to several math web sites to solve the 15 decimal place
precision problem, but failed to solve the problem. That had more to do with
the 6th degree. But I assume you are trying to accomplish something similar,
but for a 3rd degree poly.

How much data are you actually dealing with? Does it exceed 65000?
--
David


"Suzy" wrote:

I need to process a large amount of data. I would like to automatically
insert the equations for third order polynominal trendlines based on my data
into a cell so I can further use the data. I know I can fit the line, copy
the equation, paste into a cell, and then modify so it is a working equation,
but for the amount of data I have this is absurd.

I am slightly familiar with macros, but I have never written my own.

There must be an easier way

Thanks!