[Limdep Nlogit List] Error msg-Nested logit

[Gonzalez, Juan]

Hi,

 

I am running a nested logit model but the program is not letting me
specify an IVSET command. Here is the code I am using:

 

NLOGIT;     Lhs=prefer1,count,altij;

 

            Choices = TTTa,TTTb,NTTTa,NTTTb;

 

            rhs = ANG100,...; 

 

            tree=TT TT[(TTTa),(TTTb),(NTTTa,NTTTb)];;

 

            ivset:(TTTa,TTTb);

            printvc;

            Checkdata $

 

This is basically the specification provided in the NLOGIT manual to
jointly model RP and SP data. The only difference here is that I don't
have a fixed number of choices so, under LHS,  I added:

 

Count = # of options in each question

 

ALTij = Number for the alternative respondents see.  

 

I think this is the right thing to do with a variable number of choices.
Everything else is pretty much standard (I think). 

 

The error message I keep getting is :

 

  Error    71: Variable list contains a name not in the expected table.

  Error   539: Variable list: The unidentifiable string is TTTA

  Error  1092: IVSET:( list ) ... Unidentified name appears in (list)

  Error  1092: IVSET:( list ) ... Unidentified name appears in (list)

 

The error goes away if I comment the IVSET line. Can someone help me
identify what I am doing wrong? Thanks in advance for your help!

 

Juan Marcos