# Re: st: nlogit and no within-group variation [Stata 8]

 From Afridi To statalist@hsphsun2.harvard.edu Subject Re: st: nlogit and no within-group variation [Stata 8] Date Thu, 23 Jul 2009 09:58:48 -0000

```Dear all,

I read this question on the group homepage. It is few years old
question. But  i could not find answer to this question from anyone
here. I will be thankful if someone can give me some direction for such
kind of case. i  am working to a smilar case and facing same problem as
stated below.

Many thanks.

kind regards
PhD Researcher
VU Univeristy, Amsterdam
The Netherlands.
Email: msabir@feweb.vu.nl

PS.  If someone want to reply can write me in person on
afridisabir@yahoo.com

--- In statalist@yahoogroups.com, "R.E. De Hoyos" <redeho@...> wrote:
>
> [Stata 8]
>
> I am trying to estimate a nested logit using firm-level data. My
dependent
> variable (recaso1) takes three values  {1,2,3}.
>
> I nested outcomes 2 and 3 into the same group (IIA and "collapsing"
test
> suggested this).
> I have information about the firms' characteristics (and these are the
> explanatory var) but not about the outcome's characteristics.
Following
> Stata manual's instructions I -reshape-d the data (from wide to long)
to
> create a firm's id and the dichotomous variable coded as 0 for not
selected
> alternatives and 1 for the selected alternative and I set the data:
>
> gen fid = _n
> tab recaso1, gen(recaso_b)
> reshape long recaso_b, i(fid) j(wfid)
> nlogitgen resolution = recaso1(allow: Allowed, notallow: Conditioned |
> Changed)
> nlogittree recaso1 resolution
>
>   resolution       recaso1
> --------------------------
>        allow        Allowed
>     notallow      Conditioned
>                        Challenged
>
> The following occurs when estimating the model:
>
> nlogit recaso_b (recaso1 = ihh ext colusion) (resolution = ihh hist
rela syn
> imp eb2), group(fid)
>
> tree structure specified for the nested logit model
>
>         top --> bottom
>
>   resolution       recaso1
> --------------------------
>        allow       Allowed
>     notallow     Conditioned
>                       Challenged
> note: ihh omitted due to no within-group variance
> note: ext omitted due to no within-group variance
> note: colusion omitted due to no within-group variance
> no independent variables for recaso1 model
> r(102);
>
>
> Given the structure of my data I do NOT have within-group variation.
In fact
> what I want to estimate is a nested logit with -mlogit- within the
branches
> (in my case a simple -logit-), therefore I shouldn't need outcomes'
> characteristics (variation withing-groups).
>
> Is there anything that I am missing? Or is Stata'a -nlogit- subject
> to -clogit- within branches?
>
> Thanks,
>
> Rafa
>
> ________________________
> R.E. De Hoyos
> Faculty of Economics
> University of Cambridge
> CB3 9DE, UK
> www.econ.cam.ac.uk/phd/red29/
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>

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```