BOUNDS Statement

The NLIN Procedure

BOUNDS Statement

BOUNDS inequality < , ... , inequality > ;

The BOUNDS statement restrains the parameter estimates within specified bounds. In each BOUNDS statement, you can specify a series of bounds separated by commas. The series of bounds is applied simultaneously. Each bound contains a list of parameters, an inequality comparison operator, and a value. In a single-bounded expression, these three elements follow one another in the order described. The following are examples of valid single-bounded expressions:

   bounds a1-a10<=20;
   bounds c>30;
   bounds a b c > 0;

Multiple-bounded expressions are also permitted. For example,

   bounds 0<=B<=10;
   bounds 15<x1<=30;
   bounds r <= s <= p < q;

If you need to restrict an expression involving several parameters (for example, A+B<1), you can reparameterize the model so that the expression becomes a parameter.

For SAS versions 7.01 and later, lagrange multipliers are reported for all bounds that are enforced (active) when the estimation terminates. In the estimates table and in the OUTEST= data set, the Lagrange multiplier estimates are identified with names Bound1, Bound2 ... . An active bound is treated as if a restriction was applied to the set of parameters so one parameter degree of freedom is deducted. The option NOCORRECTEDDF specifies that no degrees of freedom are lost when a bound is active. Lagrange multiplier based bounds are not used for METHOD=DUD.

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