st: creating count within id & date

["Richard Hiscock" <rhiscock@netspace.net.au>]

Dear Statalist,

I have the following data structure

   id       date        var1        var2

   1        16267         x         53
   1        16267         y        106
   1        16267         y        84
   1        16267         y        90
   1        16267         z         76
   1        16267         z         65
   1        16298         x         87
   1        16298         y        76
   2        15678         x        98
   2        15678         y        98
   2         16541        x        150

etc
I wish to create identifier (visitno) 1,2,3,... for each sequential date 
within id.
I have tried to use :
sort id date
by id date: gen visitno = [_n]  which obviously doesnt produce the 
required variable
I would be greatful for solution & ?or direction to FAQ dealing with 
this
Cheers Richard



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