Sabre

ENDPOINTS

Sabre manual

Syntax: ENDPOINTS option [number1 [number2]]
where option is NO, LEFT, RIGHT or BOTH for binary models and NO or LEFT for Poisson models and number1 and number2 are optional non-negative real numbers.

Purpose:
The ENDPOINTS command determines which end-point parameters are to be included in the model. It applies only to univariate binary or univariate Poisson models.

If option is NO, then the end-point parameters are fixed at zero.

If option is BOTH, then the end-point parameters are free, and are estimated by the model. Note however that it is possible for the algorithm to fix one or both end-points at zero when a model is being fitted. If this happens, the program checks at each iteration to determine if the temporarily fixed end-point should be freed. If number1 and number2 are present, then they specify initial estimates of the left and right end-point respectively (on the odds scale).

If option is LEFT, then only the left end-point is free and estimated by the model, with the right end-point fixed at zero. If number1 is present, then it specifies the initial estimate of the left end-point (on the odds scale).

If option is RIGHT, then only the right end-point is free and estimated by the model, with the left end-point fixed at zero. If number1 is present, then it specifies the initial estimate of the right end-point (on the odds scale).

The default settings are to have both end-points in a binary model and only the left end-point in a Poisson model, with initial estimate(s) of zero. The current setting of the ENDPOINTS parameter and the initial estimates may be obtained by issuing the DISPLAY SETTINGS command.

The ENDPOINTS command has no effect on model fitting instigated using the LFIT command.