Creating a variable counting types of string variable by group

[Nobuya Fukugawa]

id	var1	var2
1	c	3
1	ab	3
1	aa	3
1	ab	3
2	abc	1
2	abc	1

How do I create var2 that counts types of string variable in var1 by id?

[Fei Wang]

Nobuya, using dataex to show the data example would be more helpful.

* Example generated by -dataex-. For more info, type help dataex
clear
input byte id str3 var1
1 "c"  
1 "ab" 
1 "aa" 
1 "ab" 
2 "abc"
2 "abc"
end

bys id (var1): egen var2 = total(var1!=var1[_n-1])

[Nick Cox]

On #2 note that the help for egen warns against use of subscripted expressions. That one will probably work, and this should certainly work.

egen tag = tag(id var1) 
egen ndistinct = total(tag), by(id)

or this

bysort id var1 : gen ndistinct = _n == 1 
by id: replace ndistinct = sum(ndistinct) 
by id: replace ndistinct = ndistinct[_N]

See also https://www.stata-journal.com/articl...article=dm0042