To follow up
. set obs 3
. gen byte coreweight1968=18
. gen float firstweight = coreweight1968 * 60468000/78028
^^^^^
. gen dummy = 1
. tab dummy, sum(firstweight)
works nicely. Seems like -tabulate, summarize- internally creates a
float to store something.
Uli
Am Dienstag, den 15.09.2009, 13:32 +0200 schrieb Ulrich Kohler:
> <>
>
> yes, I thought about that. However, the following bit shows that your
> example is not quite the problem here
>
> . set obs 3
> . gen byte coreweight1968=18
> . gen double firstweight = coreweight1968 * 60468000/78028
> . format firstweight %32.20f
> . l
>
> +-----------------------------------------------+
> | cor~1968 firstweight dummy |
> |-----------------------------------------------|
> 1. | 18 13949.14646024503963417374 1 |
> 2. | 18 13949.14646024503963417374 1 |
> 3. | 18 13949.14646024503963417374 1 |
> +-----------------------------------------------+
>
> . gen dummy = 1
> . tab dummy, sum(firstweight)
>
> | Summary of firstweight
> dummy | Mean Std. Dev. Freq.
> ------------+------------------------------------
> 1 | 13949.146 .00024815 3
> ------------+------------------------------------
> Total | 13949.146 .00024815 3
>
>
> However you are right that is should be some kind of a precision
> problem. In fact
>
> . replace firstweight = coreweight1968 * 4/3
> . tab dummy, sum(firstweight)
>
> works as expected.
>
>
> Am Dienstag, den 15.09.2009, 12:54 +0200 schrieb Martin Weiss:
> > <>
> >
> >
> > Probably a precision issue as in
> >
> > ***
> >
> > clear*
> >
> > inp double firstweight
> > 13949.1460454864
> > 13949.146248765
> > 13949.146324324
> > end
> >
> >
> > gen byte dummy=1
> >
> > su firstweight
> >
> > tab dummy, /*
> > */ sum(firstweight)
> >
> > ***
> >
> >
> >
> > HTH
> > Martin
> >
> > -----Ursprüngliche Nachricht-----
> > Von: [email protected]
> > [mailto:[email protected]] Im Auftrag von Ulrich Kohler
> > Gesendet: Dienstag, 15. September 2009 12:14
> > An: statalist
> > Betreff: st: Diffrence between sum and tabsum
> >
> > <>
> >
> > Does anybody know why -tabulate, summarize- displays a nonzero
> > standard-deviation for a variable that is a constant?
> >
> > . tab seopsu if seopsu==948, sum(firstweight)
> >
> > Cps Pr |
> > Sampl Un | Summary of firstweight
> > 5:71-73 | Mean Std. Dev. Freq.
> > ------------+------------------------------------
> > 948 | 13949.146 .00024815 3
> > ------------+------------------------------------
> > Total | 13949.146 .00024815 3
> >
> > . sum firstweight if seopsu==948
> >
> > Variable | Obs Mean Std. Dev. Min Max
> > -------------+--------------------------------------------------------
> > firstweight | 3 13949.15 0 13949.15 13949.15
> >
> > . return list
> >
> > scalars:
> > r(N) = 3
> > r(sum_w) = 3
> > r(mean) = 13949.14646024504
> > r(Var) = 0
> > r(sd) = 0
> > r(min) = 13949.14646024504
> > r(max) = 13949.14646024504
> > r(sum) = 41847.43938073512
> >
> > . d firstweight
> >
> > storage display value
> > variable name type format label variable label
> > ----------------------------------------------------------------------------
> > ------
> > firstweight double %10.0g
> >
> > . l firstweight if seopsu==948
> >
> > +-----------+
> > | firstwe~t |
> > |-----------|
> > 4256. | 13949.146 |
> > 4365. | 13949.146 |
> > 4537. | 13949.146 |
> > +-----------+
> >
> > . about
> >
> > Stata/MP 11.0 for Unix (Linux 64-bit x86-64)
> > Born 26 Aug 2009
> > Copyright (C) 1985-2009
> >
> >
> >
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