On Sun, Aug 30, 2009 at 9:15 AM, David Torres<[email protected]> wrote:
> Austin, I've looked over the code you offered and it seems that what I'm
> getting is just the xy coordinates rather than what I need. There's got to
> be a way, somehow, to have stata return a list of all the unitids that are
> within the specified radius. When I run the code I have, all I get is a
> return of the unitid on the nearest school to my 65000 tracts. However,
> within the rad10 variable, several tracts have multiple schools within my
> radius of 10 miles. I need to get all of these unitids regardless of
> whether I end up with wide or long data; I can always reshape later.
>
How about something like this:
clear
set obs 9
gen id =_n
set seed 1234
gen latitude = uniform()/2
gen longitude = uniform()/2
mata
X= st_data(.,( "latitude" , "longitude"))
X =X*(pi()/180)
dist = J(rows(X),rows(X), 0)
for (i = 1; i <=rows(X); i++) {
for (j = 1; j <=rows(X); j++) {
dist[i,j] = (1/1.609)*6372.795*(2*asin(sqrt( sin((X[i,1] ///
- X[j,1])/2)^2 + cos(X[i,1])*cos(X[j,1])*sin((X[i,2] ///
- X[j,2])/2)^2 )))
}
}
N = mm_cond(dist :<= J(rows(dist), cols(dist), 10), ///
J(rows(dist), cols(dist),1), J(rows(dist), cols(dist), 0))
st_matrix("N" ,N)
dist
end
svmat N
l
Scott
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