Number of Joinpoints

Enter the minimum and maximum number of joinpoints to fit where:

Min = 0, Max = 5, when the Grid Search method is selected.

As of Version 3.5, the default value for the maximum number of joinpoints depends on the number of data points. This value can be changed by the user, subject to having a minimum number of data points necessary to satisfy two pre-set rules:

  • A joinpoint cannot occur within a user-specified number (default: 2) of data points from the beginning or end of a series.
  • There must be at least a user-specified number (default: 2) of data points between two joinpoints.

 

The default maximum number of joinpoints is a recommendation based on the same metrics used to determine the minimum number of data points (or conversely the maximum number of joinpoints for a given number of data points). The default is based on the following recommendations:

  • At least seven data points should be observed in order to consider allowing a joinpoint.
  • There should be, on average, at least two data points between consecutive joinpoints.

 

These algorithmic recommendations lead to the following default maximum number of joinpoints.

Number of Data Points Default Maximum Number of Joinpoints
0 - 6 0
7 - 11 1
12 - 16 2
17 - 21 3
22 - 26 4
27+ 5

Note: The Grid Search Method allows a maximum of 9 joinpoints, but those runs could take quite a long time to complete.