Force all coefficients to be negative in PROC REG

I'm wondering if there's a way to force all non-intercept coefficients to be positive/negative in proc reg. If I use:

model depvar=indvar;
RESTRICT indvar<0;

Then I always get a syntax error. Looks like Proc reg only supports e开发者_开发知识库quations and not inequalities? I'm just wondering if there's any way to achieve this.

Direct from the source: Can I apply an inequality constraint to the parameters in PROC REG?

In short: no, but you can with PROC NLIN (nonlinear regression) with the BOUNDS statement.