Jerry,

This concerns me even more then. I am not missing any of the function when
I copy and paste, we are just literally copying the whole chart, which
includes the funciton, and pasting that in any other file, even the same
excel document again. I only copied the equation out seperatly to highlight
the problem I had noticed, which is that when you copy and paste the entire
chart it drops the cubic coefficient for absolutly no reason. Now if what
you are pointing out is correct, then Excel is not even computing the
Trendline equation correctly in the first place, that is even a bigger
problem. Can you verify the errors by following my steps?

"Jerry W. Lewis" wrote:

For the data you specified, the cubic coefficient should be 9.6E-09, not
6E-09. IF you are not copying the entire coefficient, that may be why Word
is dropping it. If the chart itself is failing to display the correct value,
that would be another problem altogether.

Note that you can calculate the coefficients yourself, using LINEST. Select
three adjacent cells in one row and array enter
=LINEST(ydata-100,xdata^{1,2,3},FALSE)
That will give you the cubic, quadratic, and linear coefficients for the
cubic polynomial with intercept forced to be 100.

Jerry

"Charles @ Aldenlab" wrote:

Sure....use this data

x y
1252.531345 44.0462161
1399.141231 54.03976206
1400.056416 44.5415568
1398.717824 36.45095719
1121.321671 69.02084478
1120.421493 57.35527023
1121.880135 58.10791134
1015.828469 52.80347407
842.7187937 73.74794476
755.8568419 69.50308062
841.0183109 68.54248481
560.0202985 81.17169689
503.6105019 79.47102425
560.4900412 81.38340795
281.0801761 94.02451592
252.2988083 96.7705903
281.3767037 92.81489618
0 100

Plot that data on an XY Scatter Plot in Excel 2007.

Select the series, then right click and "Add Trendline"

Use the following properties for the trendline:

Trend/Regression Type:
Polynomial - Order 3

Trendline Name:
Automatic

Check Set Intercept = 100
Check Display Equation on chart
Check Display R-squared value on chart

You will get an equation:
y = 6E-09x3 - 3E-05x2 - 0.021x + 100

Now, copy the chart and paste it into another Excel 2007 document, Word
2007, Powerpoint 2007, ect. document and note the equation. It will change
to the following:
y = - 3E-05x2 - 0.021x + 100

This is the previous equation minus the x^3 term. If you check the
Trendline properties, they are all still set as they where in the original
chart. The only way to get the equation working correctly again is to remove
then readd the trendline.

I hope you can reproduce this error, this occures on all of our Office 2007
installations here, Pro Plus and Standard about 40 copies. If there are
others in the engineering world experiencing this problem, and not noticing
it, there could be serious concequences for the projects they are working on.