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Re: st: data points within radius?


From   Scott Merryman <scott.merryman@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: data points within radius?
Date   Wed, 8 Jul 2009 10:12:28 -0500

Diego,

Do you mean something like this:


clear

input  str14 gisjoin     longitude   latitude     sch_lon    sch_lat   unitid
"G060000400100"   -124.5746   39.97379   -85.95683   31.80067   102368
"G0600010400200"   -124.5933   39.95392   -86.25552   31.30878   101107
"G0600010400300"   -124.5983   39.94619   -86.86419   33.10434   101709
"G0600010400400"   -124.6022   39.95378   -87.67984   34.73044   101736
"G0600010400500"   -124.6101   39.95397   -85.94818   32.92472   100760
"G0600010400600"   -124.6098    39.9473   -86.16864   32.38251   101958
"G0600010400700"   -124.6177   39.94698   -86.99479   33.36999   100919
"G0600010400800"   -124.6299   39.95023   -87.55314   33.09406   102067
"G0600010400900"   -124.6261   39.94432   -85.83498   31.29919   101143
"G0600010401000"   -124.617   39.93631   -85.68978   32.42277   102216
"G0600010401100"   -124.6081    39.9358   -87.01451   32.44433   101301
"G0600010401200"   -124.6017   39.93617   -86.34469   32.34993   102313
"G0600010401300"   -124.6105    39.9232   -86.31091   32.37661   102359
"G0600010401400"   -124.6178    39.9257   -86.79467   33.46106   102049
"G0600010401500"   -124.6257    39.9277    -87.0184   32.42337   101073
end

matrix dist = J(15,15,0)
matrix id_2100_ = J(15,15,0)
forv j = 1/15 {
	forv i = 1/15 {
		matrix dist[`j',`i'] = sqrt( (69.1*(sch_lat[`i'] - latitude[`j']))^2 ///
 + (69.1*(sch_lon[`i'] - longitude[`j']) * cos(latitude[`j']/57.3))^2)
	
	matrix id_2100_[`j',`i'] = unitid[`i']*(dist[`j',`i'] < 2100)

}
}

mat list dist
mat list id_2100_

svmat id_2100_

Given that all you gisjoin coordinates are in the Pacific Ocean off of
California and the unitids are in Alabama, you are going to need a
radius larger than 50 miles to find any matches.  In the example above
I changed the cutoff to 2100 miles.

Scott

On Tue, Jul 7, 2009 at 8:58 AM, David Torres<torresd@umich.edu> wrote:
> Austin,
>
> Thanks for the tip.  I figured there was a way to complete this
> process in a loop, but as I'm not too familiar with the intricacies of
> stata code (and don't possess a good text on it) I just waste a lot of
> time trying different things based on other code I've seen.  At any
> rate, allow me to give an example of the data I'm working with
> (already nonmatch merged and abbreviated for simplicity).
>
> input   gisjoin     longitude   latitude     sch_lon    sch_lat   unitid
> G0600010400100   -124.5746   39.97379   -85.95683   31.80067   102368
> G0600010400200   -124.5933   39.95392   -86.25552   31.30878   101107
> G0600010400300   -124.5983   39.94619   -86.86419   33.10434   101709
> G0600010400400   -124.6022   39.95378   -87.67984   34.73044   101736
> G0600010400500   -124.6101   39.95397   -85.94818   32.92472   100760
> G0600010400600   -124.6098    39.9473   -86.16864   32.38251   101958
> G0600010400700   -124.6177   39.94698   -86.99479   33.36999   100919
> G0600010400800   -124.6299   39.95023   -87.55314   33.09406   102067
> G0600010400900   -124.6261   39.94432   -85.83498   31.29919   101143
> G0600010401000   -124.617   39.93631   -85.68978   32.42277   102216
> G0600010401100   -124.6081    39.9358   -87.01451   32.44433   101301
> G0600010401200   -124.6017   39.93617   -86.34469   32.34993   102313
> G0600010401300   -124.6105    39.9232   -86.31091   32.37661   102359
> G0600010401400   -124.6178    39.9257   -86.79467   33.46106   102049
> G0600010401500   -124.6257    39.9277    -87.0184   32.42337   101073
> end
>
> The first three columns represent information from the master data, while
> the remaining three columns represent information from the using data set.
>  I'm supposing that additional variables can be excluded in this example
> since what I need is the total number of unitids--of the using data set--in
> a radius of, say, 50 miles of gisjoin--of the master data set.
>
> Thanks,
> Diego
>
> --------------------------------------------
>
> David Diego Torres, MA(Sociology)
> PhD Candidate in Sociology
>
> 2030D Population Studies Center
> University of Michigan Institute for Social Research
> Ann Arbor MI  48106-1248
> Tel 734.763.4098
> Fax 734.763.1428
> torresd at umich dot edu
>
> *
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> *   http://www.ats.ucla.edu/stat/stata/
>

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