I am shocked to find my good friend Kit Baum throwing
away 20% of his data. No doubt this profligacy
matches his research problem. In environmental science,
which I know more about,
throwing out the tails would lose all the bangs and leave
mostly whimpers, but he is doing economics, where some
of the extreme values may represent accountancy artefacts.
On -iqr-, since half the work is done, perhaps there is
a case for a formal update. I will contact the author,
Larry Hamilton, whose book's various editions have
served so many Stata users so well. (It got me started.)
But -iqr-'s main function I see as reporting. Rodrigo's
example of a -foreach- loop cycling over variables
and -summarize- results is the way to go for selection of subsets
of data.
Nick
[email protected]
Rodrigo A. Alfaro
> ///
> Wow Nick, your translation from 'demotic' can be only
> compared with the work
> of Thomas Young. Just kidding, very good job indeed!!
> Returning to the
> problem, it would be nice to get a list of return scalars in your new
> version. For the problem, the limits were the observations
> are supposed to
> be outliers can be used after for sample selection or to create new
> variables.
>
> Alternative to the procedure discussed so far, there is
> another way to
> 'deal' with the outlier (if you want to), which is cutting
> the tails "we
> trimmed firms whose total assets growth rate exceed the 90th
> percentile or
> fall short of the 10th percentile of the annual
> distribution." page 6 of
> Baum, Caglayan, Ozkan (2003), Working Paper 566, Boston College. For
> example, tdavis could use the following code to 'drop' the
> outliers that are
> above of 5th and 95th percentile of each variable:
>
> foreach x of varlist price total_assets inventories {
> gen double `x'_wo = `x'
> sum `x', d
> local u = r(p95)
> local l = r(p5)
> replace `x'_wo = . if `x'>`u'
> replace `x'_wo = . if `x'<`l'
> }
> From: "Nick Cox" <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, June 06, 2007 6:53 PM
> Subject: st: RE: RE: IQR
>
>
> >I spent a while updating -iqr- to -iqr8-.
> >
> > This was unnecessary, because -iqr- works
> > fine under version control. (How many programs
> > would run without change in other software after 16 years?)
> > Nevertheless, few Stata users will now be accustomed to reading
> > or writing Stata like this:
> >
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