07-23-2012 06:11 PM
I am attempting to estimate a nested logit model using the MDC procedure. I have run a conditional logit model using the following proc mdc statement, which works fine:
proc mdc data = base outest = ests type = clogit;
model decision = x1 x2 x3... x15 /
choice = (plan 348 341 ...);
I truncate the list of alternatives because it is huge. I would like to allow for correlation among the error terms for two types of products over which I estimate choice probabilities, so I next specify a 2-level nested logit model where the first level is the choice of type1 v. type2 and the second is choice among alternatives within type1 and type2. I do this as follows:
proc mdc data = base type = nlogit;
model decision =x1 x2 x3... x15 /
choice = (plan 347 341 ...);
utility u(1,) = x1 x2 x3... x15;
nest level(1) = (347 341... @1, 344 0 ... @2),
level(2) = (1 2 @ 1);
When I submit this statement I see the following error:
Warning: NEST statement contains redundant choices for the Level 1. See 1st MODEL statement.
I'm quite unsure what this means- I believe I've specified everything correctly, and i know for a fact that in the nest statement there are no alternatives that are in both the @1 and @2 levels which is how I'm interpreting the error. Any advice or insight would be greatly appreciated.