st: Syntax to specify clustering on a variable or turn off clustering

[Nicholas Potter <potter.nicholas@gmail.com>]

Hello -

I'm trying to write a program that will use clustering on a variable by
default, but also give the user the option to turn it off or to cluster on
a different variable. The problem is that including both "cluster(varname)"
and "nocluster" in the syntax definition results in the cluster option not
being stored.

For example:

program define regress2

syntax varlist [if] [in] [aw fw iw/] [, cluster(passthru) nocluster ]
...
if "`cluster'"=="nocluster" {
  reg yvar xvars
}
else if "`cluster'"=="" {
  reg yvar xvars, cluster(foriegn)
}
else {
  reg yvar xvars, `cluster'
}

end

This will default to cluster(foreign) regardless of whether a
cluster(varname) option is passed:

webuse auto, clear
regress2 price mpg rep78 --> program clusters on foreign
regress2 price mpg rep78, cluster(make) --> program clusters on foreign
regress2 price mpg rep78, nocluster --> no clustering is used


the second command should cluster on make instead of on foreign.

Any thoughts or recommendations? I could change nocluster to clusteroff or
something, but that wouldn't be in keeping with stata syntax convention.

Thanks,
Nick

~nap
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