Check for singleton dummy

[Varsha Vaishnav]

Hello,

When I run ivreg2 on my sample, stata does not report overidentification statistic. It mentions singleton dummies in the possible causes. How can I check for the same?

Thanks

[George Ford]

I was unable to replicate the problem, but typically you can list the ID (or whatever tells you what you're looking for) using

list ID if !e(sample)

If that doesn't work, then estimate by reg and try that.

[George Ford]

or,

gen insample=e(sample)

and look for 0's.

[Varsha Vaishnav]

Thank you, George.