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RE: st: RE: two STATA questions


From   "Ni Frank" <frankflying03@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: RE: two STATA questions
Date   Tue, 27 Feb 2007 01:48:50 -0500

Hi Nick,

Oh,I see. By the way, the "drop if count" should be "drop if count==0", right? I have tried your method. It works. Thanks very much!

Yours sincerely,
Frank



From: "Nick Cox" <n.j.cox@durham.ac.uk>
Reply-To: statalist@hsphsun2.harvard.edu
To: <statalist@hsphsun2.harvard.edu>
Subject: st: RE: two STATA questions
Date: Tue, 27 Feb 2007 01:25:37 -0000

Answers sprinkled below.

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

Ni Frank

> Hi, I have two basic questions on STATA.

Please read, learn and inwardly digest
http://www.stata.com/support/faqs/res/statalist.html#spell

Also, there is no reason to invent your own conventions.
Write -drop- and -keep- below. This is explained in the FAQ
(again).

> 1) There are 50 varialbes, w05100, w05200,....,w10000. We
> want to DROP
> those obversations for which at least one of the above
> variables takes
> value of 0.  When I use "drop if w*==0, it said "W* invalid name".
> Does anybody know what's wrong?

That's illegal. You can't put a wildcard there after -if-. An expression
can go there, but a wildcard doesn't qualify as an expression.

Here is one way to do it.

gen byte count = 0

qui forval i = 5100(100)10000 {
	replace count = count + (w0`v' == 0)
}

drop if count

> 2)  Now, if we want to KEEP those obersvations for which at least one
> of the variables w05100, w05200, ....,w09900 takes value of 0. How to
> do that?

It's the same story, except for -keep- instead of -drop-.

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