From an old post by Gabor
http://tolstoy.newcastle.edu.au/R/help/04/01/0147.html
apply
(outer
(landmark_c,t(store_c),"-"),c(1,4),function(x)sqrt(sum(diag(x*x))))
On 7 Dec 2009, at 10:58PM, dolar wrote:
Hi there
I have two tables, with longitudinal and latitudinal coordinates.
what I
want is a cross table between each coordinate, to find the distance
between
each building and different landmarks
I currently have this nested loop which is fine for when i have 10
stores of
interest, against 200 other landmarks and uses pythagarus to find the
distance
for(i in 1:nrow(store_c)){
landmark_store_cross_tab$foo=landmark_c$landmark_name
for (j in 1:nrow(landmark_c)){
landmark_store_cross_tab[j,i+1]=sqrt((landmark_c$x[j]-store_c$x[i])^2
+(landmark_c$y[j]-store_c$y[i])^2)/1000
}
names(landmark_store_cross_tab)[i+1]=store_c$store_name[i]
}
can someone suggest how I can make this faster?
I am hoping to use one of the apply functions
Thanks
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