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Re: st: Re: Nearstat version


From   "P. Wilner Jeanty" <pwjeanty@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Re: Nearstat version
Date   Mon, 6 Feb 2012 13:23:14 -0600

Nick and Brendan,

Thanks for the comments and suggestions upon which I will cogitate for
further improvements of -nearstat-.

Wilner

On Mon, Feb 6, 2012 at 11:41 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> In general I support programmers' rights (my program, my decision) but I
> have to say that this sounds distinctly eccentric. So in a database of Stata
> users if several people at StataCorp have the same coordinates the distance
> between them is the distance to the nearest Stata user, say several miles
> (km) away? To me it's zero. (Whether some purposes compel me to change zero
> to  some positive tolerance is a different issue.)
>
> I'd recommend to Wilner
>
> 1. Documenting this quirk in the help if that's not done already. I guess
> most users of geographical data would regard it as a misfeature, to be
> frank.
>
> 2. Even if this default is what you want consider adding an option to
> override it.
>
> 3. In fact two options: zero means that; zero means a user-specfied
> tolerance.
>
> Nick
>
>
> On 6 Feb 2012, at 16:33, "P. Wilner Jeanty" <pwjeanty@gmail.com> wrote:
>
>> 2012/2/5 Rüdiger Vollmeier <ruediger.vollmeier@googlemail.com>:
>>>
>>> Thanks a lot for the good advice how to run the program.
>>>
>>> I ve got one question regarding the programming: It seems that in case
>>> of non-identical observations with identical longitude and latitude,
>>> the programs does not return the distance 0 but calculates the
>>> shortest distance to non-identical latitude and longitudes. Am I
>>> right? This is surprising and, I guess, for many users not desired. Is
>>> it possible to change that (such that the distance 0 will be returned
>>> in these cases)?
>>
>>
>>
>> This is a legitimate behavior by the program. Because it does not
>> stand to reason that two different locations have identical latitudes
>> and longitudes, -nearstat- thinks that it is computing the distance
>> between an observation and itself. In order to identify the nearest
>> neighbors (1st, 2nd, 3rd, and so forth), distance computed from an
>> observation to itself is intentionally set to missing as part of the
>> programming process. Ruediger's case where non-identical observations
>> have identical latitudes and longitudes is an unusual one. As a
>> result, I don't intend to modify -nearstat- to allow for it, at least
>> not now, unless many users want this change to be made. Without more
>> information, I find it odd that non-identical observations or areal
>> units have identical latitudes and longitudes.
>>
>> FYI, a new version of -nearstat- with Mata code compiled in Stata 10.1
>> has been submitted to SSC.
>>
>>
>
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