![]() > I expect there's a straightforward way to do this. > (b) sum up the results of these computations, returning a value which I, doing computations involving variables > For every observation i, I think I need to > loop over all observation and sum up the results. > latitude for each observation, and computation of the distance from any While the GEODIST procedure allows users to calculate as the crow flies, straightline distances, SAS does not directly. ![]() > distances between observation i and all j n.e. > The variable created is a weighted sum of the inverse of geographical > I have need to use information from all observations (about 1800 of > running sum, take a look at -help sum()-. Downloadable geodist calculates geographical distances by measuring the length of the shortest path between two points along the surface of a mathematical. ![]() > If you want the total of a variable, look at -egen, total(). > the easiest is simply to -generate- a sum by adding values with a "+" Description Given two sets of points on the earths surface in latitude, longitude form, returns the geodetic distances in meters between corresponding points. > Creating sums can mean different things in Stata. sum up the results of these computations,". > to all other observations (or more generally, to some set of other > observation, the sum I'm talking about is of measurements made relative > Thanks, I guess I was unclear on this aspect of the problem. > To: Subject: st: RE: RE: AW: Creating index relative to other observations > On Fri, at 7:49 AM, Frederick Guy wrote: > geodist lat lon `=lat' `=lon' if _n != `i', gen(d) > * This example require my -geodist- program available on SSC > is then updated with the value of the sum plus the value of x2 for > according to the distance to `i' and summed. > distance from observation `i' to all others (distance will be missing > Perhaps the following example is close to what you are trying to do. > To: Subject: Re: st: RE: RE: RE: AW: Creating index relative to other observations If I just stack observations type i on top of observations type j, geodist doesn't like the missing values (observations type i have missing values for type j, and vice versa). Description Convert one or two rectangular objects containing lon-lat coordinates into vector or matrix of geodesic distances in metres. For each location of type i, I need to compute the distances to every location of type j. Where geodesics do not exist, the value in inf.replace is substituted for the distance in question. geodist uses a BFS to find the number and lengths of geodesics between all nodes of dat. > Robert Picard sent the code below, which works as advertised - many thanks, Robert! Now I have a slightly different problem: I have two kinds of locations in the data, i and j. geodist: R Documentation: Fund the Numbers and Lengths of Geodesics Among Nodes in a Graph Description. Geodist lat1 lon1 `=lat2' `=lon2', gen(d) ![]() Gen lon2 = -109 + (109 - 102) * uniform() whuber Trying to implement your method in R with sf. * This example require my -geodist- program available on SSC Updated version of my example the looping is over all observations of Set of observations side-to-side and it's easier to manage. To append both datasets but to do an unmatched merge. If you have two kinds of locations, then the easiest solution is not Provide approximate yet very fast distance calculations within smallĪreas (tens to a few hundred kilometres across).Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at. Implemented are Haversine, Vincenty (spherical and elliptical)), theĪnd the “reference” implementation of Karneyīe used for that.) The mapbox cheap ruler Spherical and elliptical distance measures. #> 10 10Īll outputs are distances in metres, calculated with a variety of The 'cheap' measure is inaccurate over such #> large distances, you'd likely be better using a different 'measure'.
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