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Re: st: RE: I did it! sorting with a key.


From   "Ashim Kapoor" <ashimkapoor@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: I did it! sorting with a key.
Date   Fri, 12 Sep 2008 20:19:54 +0530

Thank you Nick. Really appreciate all your effort.

Ashim.

On Fri, Sep 12, 2008 at 8:13 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> Dear Ashim:
>
> "Guys" at least in some quarters connotes males only and thus might be
> read as sexist.
>
> I have some comments on your program:
>
> 0. The exact purpose of the program needs to be documented in a help
> file. Without that readers have to guess at precisely what is intended.
>
> 1. You make -key()- optional, but your program will I think fail if no
> -key()- is provided. As the whole point of the program is to use a key,
> that option should be compulsory.
>
> 2. The use of -st_view()- within your Mata code implies that both your
> main -varlist- and the argument of -key()- should be varlists specifying
> only numeric variables. Your program will fail otherwise. It is best to
> trap any string variables early. If you ever wish to sort string
> variables, or with string variables, you would need to generalise the
> program or to write another.
>
> 3. That being so, the option -strok- is a distraction on -marksample-.
> (It is irrelevant in any case given -novarlist-.)
>
> 4. As it stands, your -marksample- always generates 1s for every
> observation. It is thus redundant as it stands, although equally it does
> no harm. The main point of using -marksample- would thus be if you
> decided to support -if- and -in- as well.
>
> 5. There is no check in your program that the number of variables in
> -varlist- and -key()- is the same.
>
> Answering also another question of yours, your program could thus start
>
> program keysortrows
>    version 9
>    syntax varlist(min=2 numeric) ,  key(varlist numeric min=2)
>
>    marksample touse, novarlist
>
>    local nv : word count `varlist'
>    local nk : word count `key'
>    if `nv' != `nk' {
>         di as err "`nv' variables, but `nk' key variables"
>           exit 198
>    }
>
>    mata:_keysortrower("`varlist'", "`key'","`touse'")
> end
>
> or
>
> program keysortrows
>    version 9
>    syntax varlist(min=2 numeric) [if] [in] ,  key(varlist numeric
> min=2)
>
>    <same stuff>
> end
>
> depending on the answer to 4.
>
> I have not checked this code.
>
> I have not looked in detail at your Mata code. I will if I get some time
> later to do it.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Ashim Kapoor
>
> I wrote a code which is the SAME as sortrows but it sorts with a KEY.
>
> Here is the ado file :-
>
>  program define keysortrows
>    version 9
>    syntax varlist(min=2) ,         ///
>    [                               ///
>        key(string)                 ///
>    ]
>
>    marksample touse, strok novarlist
>
>    mata:_keysortrower("`varlist'", "`key'","`touse'")
> end
>
> mata:
> void _keysortrower(string scalar varlist,string scalar key,string scalar
> touse)
> {
>
>         real matrix x
>
>         st_view(X,.,tokens(varlist),touse)
>         st_view(Y,.,tokens(key), touse)
>
>
>        for(i=1;i<=rows(X);i++){
>        x=(X[i,.]\Y[i,.])
>
>        x=sort(x',2)
>
>        x=x'
>        X[i,.]=x[1,.]
>        Y[i,.]=x[2,.]
>        }
> }
> end
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