I've just released an augented version of Stata's collapse command, called collapse2. The only change is that there are now four new "aggregation" operators:
first -- first observation in group
last -- last
firstnm -- first non-missing
lastnm -- last non-missing
Data must be tsset to use the operators. I find these convenient for example for converting a panel data set with annual observations to one with decadal observations where I need such variables as initial
GDP and initial population.
To install, type "ssc install collapse2". Comments welcome.
David Roodman
Center for Global Development
[email protected]
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