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Re: st: RE: RE: by and missing values question

From   Nikolaos Kanellopoulos <>
Subject   Re: st: RE: RE: by and missing values question
Date   Tue, 12 May 2009 06:30:19 +0000 (GMT)


Thanks for all the comments-suggestions


----- Original Message ----
From: Nick Cox <>
Sent: Monday, May 11, 2009 4:06:14 PM
Subject: st: RE: RE: by and missing values question

That was an exaggeration on my part. You could set it up so that the
total results were only issued (say) on the last call. But I still
suggest just issuing it twice. -help byable- points to details, either


Nick Cox

Question [2] is a good question. You could engineer your program so that
it always returned total results too, but the effect would inevitably be
that it did that every time round the loop. In practice I'd tend to
issue the command twice, once without and once with -by:-. 

Nikolaos Kanellopoulos

I have written the following very simple program

cap pr drop logdiff
program define logdiff , rclass byable(recall)

    syntax varlist(min=2 max=2) [if] [in] [fweight aweight] 

    version 8.0
    tempvar dif
    marksample touse 
    qui count 
    local N = r(N)

    qui count if `touse'
    if r(N) == 0 error 2000
    local n = r(N)

    qui gen `dif' = (`n'/`N')*abs(ln(`2') - ln(`1'))  if `touse'    
    qui su  `dif' if `touse' [`weight'`exp'] , meanonly
    loc diff = r(mean)
    di as text "Log Difference: " as result `diff'
    return scalar diff = `diff'
    return local N = `N'
    return local n = `n'

My questions are:

[1] How can I return the results for all categories when I use the by
option and not only for the last category?

[2] How can I display and return the results for the total of a category
when I use the by option? i.e. return the same results as without the by

[3] How can I exclude the missing values from my estimations both when I
use and not use the by option?

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