Use the Knotted Spline Effect option to have JMP fit a segmentation of smooth polynomials to a specified effect. When you select this attribute, a window appears, enabling you to specify the number of knot points. (Knotted splines are only implemented for main-effect continuous terms.)
Knotted splines are parsimonious, adding only k – 2 terms for curvature for k knot points.
1.
Select Help > Sample Data Library and open Growth.jmp.
2.
Select Analyze > Fit Model.
Fit Model Launch Window
3.
Select the ratio column and click Y.
4.
Select the age column and click Add.
5.
Select age in the Effects pane and select Attributes > Knotted Spline Effect.
7.
Click Run.
9.
Click the Add Column button twice to produce a total of three columns.
10.
11.
Values for the Custom Test for Curvature
13.
Click Done.
The report in Curvature Report appears. The small Prob > F value indicates that there is curvature.
Curvature Report

Help created on 9/19/2017