S Curves

[Guest]

I want to spread a value over a range of dates as an "S-Curve" with the
ability to skew the distribution. What is the best way of doing this, please?

 

[Guest]

You can try the Trend function. You will need the analysis tool pack. It will
perform a polynomial regression on a set of values.

HTH

 

[Michael R Middleton]

TREND is a built-in worksheet function. (You don't need Analysis ToolPak to
use it.) To go beyond linear regression, you could use xdata^{1,2,3} as the
x-data range in TREND, array-entered using Control+Shift+Enter.

The Regression tool of the Analysis ToolPak will perform polynomial
regression if you use x, x^2, and x^3 values (adjacent columns on a
worksheet) as the X-range.

Or, construct an XY (Scatter) chart with some hypothetical Y values, and use
Add Trendline (polynomial of order 3) to get a smooth curve approximately
through the points.

- Mike

www.mikemiddleton.com

 

[Jerry W. Lewis]

The adequacy of a polynomial approximation depends on what will be done
with it. While a polynomial may approximate the center quite well, an
"S Curve" usually refers to a bounded function with zero first
derivatives at +/- infinity, while a polynomial is unbounded with
infinite first derivatives at +/- infinity.

Jerry