Hi,

Am Wed, 25 Jan 2017 10:34:47 -0800 (PST) schrieb BottleMan:

I use the exact formula that Excel displays. Here is a typical data set:
x-Axis Y-axis
1.2 0.5
1.6 1
2.4 1.5
3.6 2
4.8 1.5
6 1
7.2 0.6
8 0.3
Here is the formula Excel displays:
y = 0.0046x4 - 0.0455x3 - 0.0981x2 + 1.5795x - 1.1698 with R² = 0.9843
Here are the values I get when I use the formula on the same x-values to calculate the Y-values:
x-Axis Y-axis
1.2 0.54
1.6 1.07
2.4 2.20
3.6 3.56
4.8 5.08
6 7.31
7.2 6.98
8 -18.11
That is even though the curve that Excel draws hugs the values very closely. So what is going on?

try it with a higher order for the trendline formula and play around
with "Set Intercept":
With "Set Intercept" to 1 and the formula
y = 0,0002x^6 - 0,0084x^5 + 0,123x^4 - 0,8225x^3 + 2,4397x^2 - 2,3116x + 1
the result is a little bit better.


Regards
Claus B.
--
Windows10
Office 2016