Trendline Equation Accuracy

[Marcus]

Hi.

I'm having some difficulty with the equation predictor on
my charts.

I've used "trendline" to give me an equation to predict
points along a set of data I have plotted.

This gives me an accurate equation, and hence prediction,
for one plot but for my second data series the accuracy of
the equation is awful, even though the trendline closely
follows the original data series.

Does anyone know how I can get an accurate equation
prediction for all my plots?


Thanks in advance.

 

[Jerry W. Lewis]

You gave too little information for anyone to do more than guess.

The usual problems people have with Excel chart trendlines are

- Trying to calculate with the heavily rounded coefficients of the
default display - right click on the equation and format for scientific
notation with 14 decimal places, or use David Braden's VBA code to
extract the coefficients directly from the chart into cells

http://groups.google.com/[email protected]

- Using a "Line" chart instead of an "XY (Scatter)" chart. "Line" chart
is a misnomer; it has nothing to do with whether you want lines
connecting your data or not, what distinguishes it from an "XY (Scatter)
chart is that the "Line" chart ignores your x-data (except for
labeling purposes) and computes as though the x data was 1,2,3,...

Jerry