[Limdep Nlogit List] GROUPED DATA with Sample selection

[Suman Majumdar]

Hi:
I am trying to estimate a "Grouped Data Regression with sample selection."
My dependent variables are Y (for Grouped Data) and NR (for sample selection).
Now when I run the regression, I get the following error.
 
Error 49: GROUPED Y > # limits + 1. Bad data or too few limit values.
 
 
I think I am getting this error because I have missing values for Y.
I have missing values because Y is not observed when NR is 0.
I believe this is what it should be. But I don't know why I am getting this error.
 
I would appreciate any help or suggestions.
 
Thanks.
Suman