st: Covariance structures for xtmelogit with a single random effect

[Najib Mozahem <najib.mozahem@gmail.com>]

Hi,
     I am using xtmelogit on my dataset. My model has only a random intercept because a likelihood test revealed that random coefficients do not contribute significantly to the model. I want to try out several covariance structures but whenever I try any structure I get the following:

xtmelogit span1 i.type i.freq pages totalactive c.age##c.age c.time##c.time || id:, cov(unstructured) mle
Note: single-variable random-effects specification in id equation; covariance structure set to identity

On page 300 of "Multilevel and Longitudinal Modeling using stata" by Rabe-hesketh and Skrondal they fit a xtmixed model with just a random intercept using the residuals() option in order to specify an unstructured matrix, but this option does not exist for xtmelogit. Is there a way to try several covariance structures using xtmelogit?

Thanks
Najib
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