I have a exponential trendline that was generated by excel ("Add Trendline") on a chart.
I've plugged in the equation (from the "Display Equation on Chart" option, up to 14 decimals) into a spreadsheet and compared the projected values with those values projected by the GROWTH and LINEST functions. In my comparison, I noticed that the interpolated values differ.
Can anyone explain how the methods excel uses to derive these trendline equations differ? Is one method more appropriate than the other?
You might edit to show your data. I just entered some data that I made to look exponential-ish, and using Add Trendline (exponential) and GROWTH gave almost exactly the same results. There were only slightly different values, and I'd say that was due to the fact that I only used 4 digits after the decimal point when I displayed the equation on the chart.
This is assuming that you're trying to fit data that is exponential-like. In which case, LINEST would give dramatically different results, since it's trying to fit a straight line. On the other hand, if your data were basically linear and you tried using GROWTH on it, you won't get a very good fit there.