How do i approximate the value of a point on the trendline?
I created a polynomial trendline for a sales forecast. How do i figure out a
appriximate value for a point on the trendline |
Dheer,
Double-click on your trendline, go to Options - Display Equation on Chart. Once Excel displays the equation, substitute some number for X to calculate Y to get a point value. Typically, you could substitute 1, 2, 3, 4, 5, 6, 7, 8 .. . . etc. for X to get a series of corresponding Y values. If you plotted those XY values, they should mirror your trendline. ---- Regards, John Mansfield http://www.pdbook.com "Dheer" wrote: I created a polynomial trendline for a sales forecast. How do i figure out a appriximate value for a point on the trendline |
Be certain to display the coefficients in scientific notation with 14
decimal places, otherwise you will get rounded coefficients that may not produce good estimates with your data. Alternately, you can use the LINEST() and TREND() worksheet functions to estimate polynomials http://www.stfx.ca/people/bliengme/E...Polynomial.htm In Excel versions prior to 2003, LINEST uses a different algorithm that may have more numerical problems with challenging data or high order polynomials than the chart trendline. Jerry John Mansfield wrote: Dheer, Double-click on your trendline, go to Options - Display Equation on Chart. Once Excel displays the equation, substitute some number for X to calculate Y to get a point value. Typically, you could substitute 1, 2, 3, 4, 5, 6, 7, 8 . . . etc. for X to get a series of corresponding Y values. If you plotted those XY values, they should mirror your trendline. ---- Regards, John Mansfield http://www.pdbook.com "Dheer" wrote: I created a polynomial trendline for a sales forecast. How do i figure out a appriximate value for a point on the trendline |
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