Re: st: Grouped data and changing a variable

[n j cox <n.j.cox@durham.ac.uk>]

The trick used by David is explained more generally
in an FAQ:

How do I create a variable recording whether any members of a group (or 
all members of a group) possess some characteristic?

http://www.stata.com/support/faqs/data/anyall.html

Incidentally, the syntax of -egen, max()- is that it works
on an expression, and not just a variable name.

Hence

bysort a b c : egen newe = max(d == "Paper")

works, and there is no need for any intermediate variable.

Nick
n.j.cox@durham.ac.uk

Catrina Jordan wrote

I have a set of data where I need to replace a variable's content
depending if it is in a group and one of the variables contains a
certain value.

For example
a	b	c		d	e
101	1	01-May-06	Paper	1
101	1	01-May-06	Disc	0
101	1	01-May-06	Electronic	0
102	1	02-May-06	Paper	1
102	1	02-May-06	Disc	0
103	2	02-May-06	Disc	0
103	2	02-May-06	Electronic0


I know that the first three observations are in the same group (using
the egen command for variable a, b and c) and the second group is the
next two observations and so on but in each group if variable d contains
"Paper" then I want all the observations in the group for variable e
changed to a 1.  If there is no "Paper" in the group then to leave as
they are.


So to end up with
a	b	c		d	e
101	1	01-May-06	Paper	1
101	2	01-May-06	Disc	1
101	3	01-May-06	Electronic	1
102	1	02-May-06	Paper	1
102	2	02-May-06	Disc	1
103	2	02-May-06	Disc	0
103	2	02-May-06	Electronic0

and David Harrison suggested

Does the current value of e just represent -d=="Paper"-?

If so...

bysort a b c: egen newe = max(e)

(If not, -replace e = d=="Paper"- first)


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