On Fri, 20 Jan 2017 10:22:01 -0800 (PST), BottleMan wrote:

Hi everybody,

I use scatter charts and trendlines a lot to derive formulas from real data. Excel then prints the formula it used on the chart. However, when I use this formula with the same data set the values always differ and I have to massage the formula to make it represent the data. What am I doing wrong here?
Thanks for your help.

What do you mean by, "when I use this formula?"

Are you using the full precision of the constants produced by Excel?

I have found with nonlinear regression that rounding the constants can
produce results surprisingly far from the expected values.