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Trendline Equation Accuracy
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/groups?selm....microsoft.com - 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 Marcus wrote: 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. |
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