[Limdep Nlogit List] Pds specification for choice modeling with unbalanced datasets

[Iris Vanermen]

Dear Mr., Ms.,

I am trying to estimate a random parameters logit model in which the number of choice tasks differs between individuals. For this, I am trying to adjust the Pds specification with a variable indicating the number of choice cards per individual but I get following error: "Error 1081: Mismatch of # indivs. and number implied by groups" that I do not seem to be able to resolve. How should I specify Pds in case of different number of choice cards per individual?

Many thanks!
Best regards,
Iris Vanermen