BOUNDS bound1 [, bound2 ...] ;

The BOUNDS statement imposes simple boundary constraints on the parameter estimates. BOUNDS statement constraints refer to the parameters estimated by the COUNTREG procedure. You can specify any number of BOUNDS statements.

Each bound is composed of parameter names, constants, and inequality operators:

item operator item [ operator item [ operator item ...] ]

Each item is a constant, a parameter name, or a list of parameter names. Each operator is ’<’, ’>’, ’<=’, or ’>=’. Parameter names are as shown in the ESTIMATE column of the “Parameter Estimates” table.

You can use both the BOUNDS statement and the RESTRICT statement to impose boundary constraints; however, the BOUNDS statement provides a simpler syntax for specifying these kinds of constraints. See the section RESTRICT Statement as well.

The following BOUNDS statement constrains the estimates of the parameter for z to be negative, the parameters for x1 through x10 to be between zero and one, and the parameter for x1 in the zero-inflation model to be less than one. The following example illustrates the use of parameter lists to specify boundary constraints:

   bounds z < 0,
          0 < x1-x10 < 1,
          Inf_x1 < 1;