st: marginsplot error: margins not uniquely identified

[Molly Moore Jeffery <moor0281@umn.edu>]

I'm having trouble using -marginsplot- (Stata version 12.1). I get the following error message: "_marg_save has a problem.  Margins not uniquely identified. r(9999);"

The -margins- command itself works exactly as expected. I have a factor variable with five levels interacted with a binary participation variable. These two variables are included in the model as i.years##i.participation. The margins command -margins years#participation- produces a list of 10 predicted values, as desired. I would like to create a plot like the one used to illustrate -marginsplot- on the Stata site: http://www.stata.com/stata12/margins-plots/ (see the first plot of agegrp#sex). 

I've tried just typing -marginsplot-, as in the example code. 

I've also tried specifying the dimensions: - marginsplot, xdimension(years) plotdimension(participation)-

In both cases, I get the same error message "Margins not uniquely identified"

I haven't found any reference to this error code. Does anyone have any ideas what I might be doing wrong?

Thanks very much for the help.






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