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Re: st: RE: drop duplicates within variable with -by- option

From   David Torres <>
Subject   Re: st: RE: drop duplicates within variable with -by- option
Date   Mon, 16 May 2011 12:05:57 -0400

As always, Nick, you help so much.  Couldn't be more clear.

David Diego Torres, MA(Sociology)
PhD Candidate in Sociology

2044 Population Studies Center
University of Michigan Institute for Social Research
Ann Arbor MI  48106-1248
Tel 734.763.4098
Fax 734.763.1428
torresd at umich dot edu

Quoting Nick Cox <>:

The "by ID" element is not a problem, nor does it call for special action.

Suppose you are looking for duplicates on -x- and -y- and there is also the idea that you are checking for these within -ID-. The identifier variable does not have any special role here. You just want to look for -duplicates- on three variables, e.g.

. duplicates list ID x y

That is, -duplicates- is indifferent to the special meaning of any identifier variable.

If this does not make things clear, show us a specific example of what you want

[author of -duplicates-]

David Torres

I have data in long format and need to drop duplicate observations
within a variable by ID.  I've looked at the -duplicates- command and
it doesn't seem to help me get what I want.

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