|From||Kit Baum <firstname.lastname@example.org>|
|Subject||st: re: inequality constraints for ARCH/GARCH parameters|
|Date||Mon, 26 Jan 2004 12:23:34 -0500|
You are correct. Stata only accepts linear constraints, and inequalities do not qualify. Sometimes, in other contexts, you can get what you wish by a reparameterisation of the model, for example, by using logarithms to ensure that a parameter of interest remains positive. I've no idea if that makes sense here. Another possibility is that your model is just not suitable for your data, so that no amount of bending, twisting or pushing can improve much on what you get unconstrained.