I strongly agree with Svend's general stance here. This is not
a stupid question, and it requires some Stata technique.
I offer a condensation to one line:
bysort id (analt): keep if episodi[1] == 1 & analt > 2001
Under -by-, with the sort order specified, the subscript [1] refers to
the first year observed. This device cuts out the creation of extra
variables.
Nick
[email protected]
Svend Juul
Catia wrote:
I have a simple and stupid problem to selection some variables,
but I don't know as to resolve this problem:
I have this dataset
id analt episodi
1 1999 1
1 2002 2
2 2002 1
2 2003 2
2 2003 3
3 2004 1
3 2005 2
I want to selection all the id that analt>2001 & the first
episodi start with ==1, so I want to take id 2 and id 3
id analt episodi
2 2002 1
2 2002 2
3 2004 1
3 2005 2
---------------------------------------------------------
Your question is about keeping observations, not variables.
You can use the -egen min()- function to create a variable
that is constant for each id:
sort id analt episodi
by id: egen firstyear = min(analt)
by id: egen firstepi = min(episodi)
keep if firstyear>2001 & firstepi==1
The problem is not stupid, it is just a matter of experience.
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