st: marginsplot error, with continuous variable and factor variables

["Valle-Painter.Carla" <Carla.Valle-Painter@cic.gc.ca>]

Hi,

I am getting an error from marginsplot and I cannot understand what it means:

I am using Stata/IC 12.0

I estimated a logit model, with many independent variables which are factor variables, and a few continuous variables.

I wish to do a marginsplot of a dummy variable (Qc) across the values of one of the continuous variables.  I wanted to do this setting the factor variables at particular levels, rather than setting them "atmeans" or "asobserved"

So I ran the following command (note etc. etc. means there are other variables set at particular values that I am not listing here):

     . margins Qc, at(pgrcount =3D (0 (1) 18) sex=3D2 lis5tiles7=3 agecats=3 etc. etc.)

where pgrcount is my continuous var (really it is a count), ranging from 0 to 18.

I do get the margins for this, and then try to run the marginsplot as follows:
 
     . marginsplot, xdimension(pgrcount) xlabel(0 (1) 18)

But I get this error message:

Variables that uniquely identify margins: pgrcount Qc uslist :_at15 _m1:
_marg_save has a problem.  Margins not uniquely identified.
r(9999);

Thanks in advance to anyone who can throw some light on this.

Carla 

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