----- Original Message -----
From: "david reinstein" <[email protected]>
To: <[email protected]>
Sent: Wednesday, July 16, 2003 7:32 PM
Subject: st: xtsum -- meaning of within "min" and "max"
> The "min" and "max" part of the within column of xtsum
> confuses me -- it must be some sort of difference, but
> I cant figure out what! It gives strange fractional
> values for 0,1 variables, gives absurdly large or
> small values in some cases, sometimes gives negative
> values, but gives only positive values for an income
> variable.
> -Anyone know what this is doing?
>
The within transformation demeans the data. In particular, it substracts
the group mean and then adds in the overall mean to the series.
Try this:
. use http://www.stata-press.com/data/r8/grunfeld.dta
. by com: egen double invest_bar = mean(invest)
. egen double invest_bar2 = mean(invest)
. gen double invest_demeaned = invest - invest_bar + invest_bar2
. xtsum invest
Variable | Mean Std. Dev. Min Max |
Observations
-----------------+--------------------------------------------+-------------
---
invest overall | 145.9583 216.8753 .93 1486.7 | N =
200
between | 198.8242 3.0845 608.02 | n =
10
within | 106.1986 -204.3617 1024.638 | T =
20
. sum invest_demeaned
Variable | Obs Mean Std. Dev. Min Max
-------------+--------------------------------------------------------
invest_dem~d | 200 145.9583 106.1986 -204.3617 1024.638
Hope this helps,
Scott
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