Let Me Count the Ways, 1 2 3

Somebody asked me this morning if it is possible to generate a variable in an EXISTING stata data set containing counts, from 1 to n.

Yes, its possible, the command is:

gen varname=sum(1)

you can also have a series of variables containing, 2, 4, 6, n+2…The command is

gen varname=sum(2)

suppose, you do not want to start with 1, then

gen varname=sum(1) + 1

Suppose you have a roster data set with family members as observation and with specific family ids tagging the members of a family, and say you want to order the members, with count=1 for the youngest…Try running the commands

sort family_id age

by family_id: gen varname=sum(1)

Try running the gen ____=sum(1) command in a blank data set and see what you will get.  the answer isnt surprising :)