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Re: st: Efficiently run three loops (or do without them)


From   Eva Poen <eva.poen@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Efficiently run three loops (or do without them)
Date   Mon, 13 Apr 2009 13:52:07 +0100

Ronnie,

this is difficult to answer without knowing what you mean by "run my
checks". There are some tools out there to detect outliers; use
-findit outliers- to see what's around.

Whether or not you need nested loops will depend on whether or not
your checks need to know the actual value of fup_pdt and fup_unit. The
-preserve- and -keep- thing will slow things down, and you may be able
to do without it (by just using if conditions in your code).

But, really, we need some more information to be able to help.

Eva


2009/4/13 Ronnie Babigumira <rb.glists@gmail.com>:
> Dear list
> I have quarterly data that looks like this
>
>      qtr   houscode   fup_pdt   fup_unit   fup_qtycoll
>        1        562        23          2            50
>        1        570       628          2             2
>        1        573       628        201            10
>        1        573       628          2             2
>        1        576       628        201             5
>        1        576       628        201            20
>        1        577       628          2             1
>        1        578       628          2             1
>        1        590        34         26            60
>        1        595        34         26           200
>
> For each quarter, I would like to identify "strange" values (outliers) in
> the variable fup_qtycoll
> (simply to rule out data entry error).
>
> This would be done for the different fup_pdt and fup_unit combinations
>
> My initial idea is that I would have to do it in three -foreach- loops, be
> something along the lines
> (this does not work since I need to -preserve- before -keep-ing, which I
> would like to avoid, and it
> is not by quarter yet)
>
> levelsof fup_pdt, local(fupdts)
> foreach i of local fupdts {
>                keep if fup_pdt == `i'
>                levelsof fup_unit, local(fupunits)
>                foreach j of local j {
>                        keep if fup_unit == `j'
>                        *** run my checks and other stuff
>            }
> }
>
> I would appreciate some help on how I can do this efficiently
>
> Ronnie

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