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Re: st: tau-c on Stata


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: tau-c on Stata
Date   Thu, 31 May 2012 01:21:31 +0100

The code was probably mangled by your mailer. "di" should always start
a new line. In particular,

scalar `tauc' = r(score) * (2 * `m'/(`N'^2 * (`m' - 1)))

di _n as txt " tau_c = " as res %8.4f `tauc'

should be two distinct lines. Edit the .ado file, -discard- and try again.

Nick

On Thu, May 31, 2012 at 1:09 AM, Thomas Didier
<thomas.didier@mail.mcgill.ca> wrote:
> Many thanks for your response.
>
> 1) I run the tauc programming code.
> 2) I type "tauc var1 var2" (both variables are ordinal)
> 3) error message says:
>
> invalid 'di'
> r(198);
>
> Am I doing anything wrong?
>
> Thomas
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
> Sent: 30 mai 2012 03:54
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: tau-c on Stata
>
> Some refinements:
>
> program define tauc, rclass
> syntax varlist(numeric min=2 max=2) [if] [in]
>
> quietly {
>        marksample touse
>        count if `touse'
>        if r(N) == 0 error 2000
>        if r(N) < 3  error 2001
>        local N = r(N)
>
>        tokenize "`varlist'"
>        if "`1'" == "`2'" {
>            di as err "two different variables required"
>            exit 102
>        }
>
>        tab `1' if `touse'
>        local m1 = r(r)
>        tab `2' if `touse'
>        local m2 = r(r)
>        local m = min(`m1', `m2')
>        ktau `1' `2' if `touse'
> }
>
> tempname tauc
> scalar `tauc' = r(score) * (2 * `m'/(`N'^2 * (`m' - 1))) di _n as txt " tau_c = " as res %8.4f `tauc'
>
> return scalar tau_c = `tauc'
> end
>
> Main changes:
>
> 1. Steve's program allows -if- and -in-, but ignores them.
>
> 2. If the varlist is a wildcard, arguments `1' and `2' will not be as desired.
>
> 3. Some checking for inadequate sample size. Should probably go further.
>
> Nick
>
> On Wed, May 30, 2012 at 4:01 AM, Steve Samuels <sjsamuels@gmail.com> wrote:
>
>> The post you referred to was from Roger Newson.
>> Here's a bootstrapped version of Roger's code.
>>
>> **************CODE BEGINS************* capture program drop _all
>> program define tauc, rclass syntax varlist(min=2 max=2) [if] [in] if
>> `"`1'"'== `"`2'"' {
>>     di as error "Error: Two different variables required"
>>     exit 102
>> }
>> tempname v1 v2 m1 m2 m score N tauc
>> gen `v1' = `1'
>> gen `v2' = `2'
>> sum `v1'
>> tab `v1' if !missing(`v2')
>> scal `m1'=r(r)
>> tab `v2' if !missing(`v1')
>> scal `m2'=r(r)
>> scal `m'=min(`m1',`m2')
>> qui ktau `v1' `v2'
>> return list
>> scalar `score'=r(score)
>> scal `N'=r(N)
>> local tauc= `score'*(2*`m'/(`N'^2*(`m'-1))) return scalar tau_c =
>> `tauc'
>> end
>>
>> sysuse auto, clear
>> bootstrap tau_c = r(tau_c), reps(50): tauc trunk foreign estat
>> bootstrap, all
>>
>> ***************CODE ENDS************
>>
>
>  On May 29, 2012, at 8:53 PM, Thomas Didier wrote:
>
> Is there a command or a plug-in for Stata to estimate Kendall tau-c? A response to a 2008 question
> (http://www.stata.com/statalist/archive/2008-08/msg00300.html)
> provided a "manual" way to make the calculation; this works but takes some time and doesn't provide a level of statistical significance (ASE). Apparently tau-c is a routine estimation on SPSS and I hope I can find an equivalent on Stata.
>
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