Distance Matrix from Haversines Formula

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CharlieEVIEWS
Posts: 202
Joined: Tue Jul 17, 2012 9:47 am

Distance Matrix from Haversines Formula

Postby CharlieEVIEWS » Sat Feb 21, 2015 8:20 pm

A program to compute (symmetric) distance matrices (diag=NA) from Haversines formula with two input series of (decimal) latitude and longtitudes:

Code: Select all

if @obs(latitude)<>@obs(longitude) then
   @uiprompt("Error: Lat and Long not same size")
endif
matrix(@obs(latitude),@obs(longitude)) distance_haversine   
genr lat_rad = latitude*(@acos(-1)/180)
genr lon_rad = longitude*(@acos(-1)/180)
for !b = 1 to @obs(latitude)
   for !a = 1 to @obs(latitude)
      if !a=!b then
         distance_haversine(!b,!a)=NA
      else
         !dlat = lat_rad(!a)-lat_rad(!b)
         !dlon = lon_rad(!a)-lon_rad(!b)
         !temp = ((@sin(!dlat/2))^2)+(@cos(lat_rad(!a))*@cos(lat_rad(!b))*(@sin(!dlon/2))^2)
         !temp2 = 2*@atan((({!temp})^0.5)/((1-{!temp})^0.5))
         !r=6371 'radius of eath in KM
         distance_haversine(!b,!a)=!r*!temp2
      endif
   next
next


Any questions, please don't hestiate to ask. I intend to post a few more spatial routines in the future (next up - various distance matrices): if anybody has any requests (on distance matrices or spatial estimators), please post below any of the threads or send a PM through this forum.

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