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st: RE: possible to combine nmissing with tabstat?


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: possible to combine nmissing with tabstat?
Date   Mon, 14 Jun 2004 15:32:36 +0100

-nmissing- is a user-written command, 
last published in Stata Journal 3(4) 
2003, so far as I can see. 

-tabstat- is an official Stata command. 

What you tried cannot be expected to 
work. The -s()- option of -tabstat- just 
accepts items from a menu indicating statistics 
to be calculated within -tabstat-. What 
you tried would only work in these 
circumstances: that if -tabstat- didn't 
recognise what you asked for, it then 
would try to find a command with the 
same name and use its results in tabulation. 
I see that this idea makes sense from your point 
of view, but it is essentially impossible to program 
without knowing what kinds of results 
would be returned by the program called, and 
arguably it is bad design in any case. 

However, what you want would be 
possible to program in a different way, if 
StataCorp were to extend the set of statistics
provided to include the number of missing 
values. That would, however, require some 
restructuring of -tabstat- and arguably it 
is, again, bad design in any case, the main 
point being that -tabstat- has a clear focus
as a wrapper for -summarize-. 

Loosely similar comments apply to -tabulate- 
and -table-. 

A cruder alternative is to cut and paste
output from -nmissing- to go alongside 
outpot from -tabstat-. Clearly that is 
not a very attractive solution. 

A better alternative is to learn to 
use -tabdisp- to get what you want. In 
your example, the code might look like 

egen n = sum(1), by(DURSTAY DETMETH) 
egen nmissing, sum(mi(WEEKDELAY)), by(DURSTAY DETMETH) 
egen mean = mean(WEEKDELAY), by(DURSTAY DETMETH) 
tabdisp DURSTAY DETMETH , c(mean n nmissing) 

There is some discussion of related problems 
in 

Problems with tables, Part I. Stata Journal
3(3):309--324 (2003)

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

A.M. Vos

> I just found 'nmissing' and I hoped it was possible to use that in
> combination with
> tabstat, but it appeared not to. For instance, my syntax reads:
> 
> by DURSTAY DETMETH: tabstat WEEKDELAY, s(mean n)
> 
> and I would like to say:
> 
> by DURSTAY DETMETH: tabstat WEEKDELAY, s( mean n nmissing)
> that is, for each combination of durstay and detmeth 
> obtaining the mean
> delay in
> weeks, the number of observations on which the mean was 
> calculated, and
> the number
> of observations with a missing value on weekdelay.
> 
> it would also be nice if 'nmissing' could be used in combination with
> table and tabulate.
> would this be possible?

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