![]() Suppose you want the weighted sum of inverseĭistances (assuming none are zero) then you could just: Type j, you should not create that many new variables at once, toĬonserve memory. Store distances if you only want summary stats across locations of Of type j stored on the type i obs, you will need Nj new variables to Suppose your location variables are xi,yi,xj,yj and you have Ni obs of Variable names must be distinct across the two datasets. ![]() Strategy (merging on _n rather than any variables) is that all the The crucial detail to remember with an unmatched merge Single observation from the first, but this is understandably lessĮfficient. Published 2009 in the JHE-see also Appendix A ofĭistance weights) as a way to have two datasets in memory at once Īnother way is to repeatedly merge or append a second dataset onto a Name came later the approach was developed in 2003 for a paper Package for any of those spherical approximate computations seems likeĪs far as I know, the unmatched merge approach was first promulgated ![]() Plus, the formula in that message is the weakest of many alternatives Lat/lon occupies a large fraction of msg00473's code, but need not Īll the calculations could be telescoped into one line (it's justĮasier to break it up), and the local macros are mostly unnecessary. Note also the calculation of distance (using an approximation thatĪssumes the Earth is a sphere see -vincenty- on SSC for anĪlternative) between two points on Earth measured in decimal degrees There are numerous examples addressing your need in the Archives, e.g.: Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at. ![]()
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