Agreed on the trend line part. It does assume that the formula of the best
line is desired. This is why I gave the Slope and Intercept formulas which
can be used on any two points. Using these formulas a linear formula can be
created for each point to the next point in the series. This will require
more calculations but it will work. Depends on what the user wants. I have
done something similar using both linear and polynomial regression (Trend
Formula) with success.
--
HTH...

Jim Thomlinson


"Tom Ogilvy" wrote:

Just a thought, but
that wouldn't work for the situation described/asked for unless the data was
linear and fell exactly on the trend line.



--
Regards,
Tom Ogilvy



"Jim Thomlinson" wrote in message
...
In order to come up with the interpolation formula (the easy way) just
graph
the source data and add a linear trend line. Right click the trend line
and
one of the options is to add the formula to the trend line. This will give
you the formula of the best line through all of the points on the graph.
If
you wanted to interpolate between any two point look at the slope() and
intercept() formulas. Using these you should be able to create the Y=aX +
b
formulas for each set of points.
--
HTH...

Jim Thomlinson


"Metalmaniac" wrote:

Hello,

I am trying to create a formula that will lookup values in a column and
find
those values in another column and then place the value in the row next
to it
in a specific cell. So far this works with the formula
(=VLOOKUP(I6,$D$11:$E$223,2)). Now most of the time the value for cell
I6
(thru I n) will not be found in the list ($D$11:$E$223) so I want to
revise
the formula to do one of two things:

1. Always "interpolate" between points even when an exact match is found
in
($D$11:$E$223)

2. When the value for cell I6 (thru I n) is not found then find the
values
less than and greater than I6 and interpolate between the two points a
value
based on the slope of the function defined by the two sets of
corresponding
data.


this is driving me insane!!!! Please help me! I have 20 years of data
to
enter and if I do it manually it will take 20 years.