Dear Eric,

The error is coming from a single PSU stratum. In these situations, the R "survey" package used by DHS.rates would give you this error. Functions from the survey package are used in developing the "chmort" but not in the "chmortp". This is why you did not see the problem in the chmortp function. The good news is that the error message indicated which stratum had this issue. A quick solution for this problem would be to combine stratum one with another stratum, let's say stratum 2. I assume both are in the same region, one is urban and the other is rural. Once you do this you will get rid of the single psu stratum and the code should work properly.

Best wishes,
Mahmoud