[R] Calculate Distance and Aggregate Data?

[Gabor Grothendieck]

Assume that gcirc(x,y) takes two 2-vectors which are the latitude and
longitude of x and the latitude and longitude of y and produces the
the greatest circle distance in kilometers between them.

# read in the data as a matrix
d <- as.matrix( read.csv(myfile) )

# vectorize gcirc, i.e. allow it to have args which are matrices
# with one coordinate per row.  The first two lines of this
# function optionally allow either arg to have 1 row even when the
# other does not
gcirc.vec <- function(x,y) {
   if (nrow(x) == 1) x <- matrix(x, nrow(y), ncol(x), byrow=T)
   if (nrow(y) == 1) y <- matrix(y, nrow(x), ncol(y), byrow=T)
   mapply(function(ii,jj) gcirc(x[ii,],y[ii,]), 1:nrow(x), 1:nrow(y))
}

# and perform two applies:

f <- function(x, v) sum( d[ gcirc.vec(t(x[2:3]),d[,2:3]) < 2, v ] )

apply(d,1,f,"pop")
apply(d,1,f,"dwell")

---
Date:   Tue, 24 Feb 2004 9:58:45 -0500 
From:   <dsheuman at rogers.com>
To:   <R-help at stat.math.ethz.ch> 
Subject:   [R] Calculate Distance and Aggregate Data? 

 
Hi all,

I've been struggling learning R and need to turn to the list again.

I've got a dataset (comma-delimited file) with the following fields: recid, latitude, longitude, population, dwelling and age. For each observation, I'd like to calculate the total number of people and dwellings and average age within 2 k.m. Distance could be Euclidean, however, a proper distance calculation (great circle route) is best.

Any assistance would be appreciated.

Thanks,

Danny


--------------
Sample Data
--------------
recid,lat,long,pop,dwell,age
10010265,47.5971174,-52.7039227,584,219,38
10010260,47.5846616,-52.7039147,488,188,34
10010263,47.5936538,-52.7037037,605,232,43
10010287,47.5739426,-52.7035365,548,256,29
10010290,47.5703333,-52.703182,559,336,36
10010284,47.5800199,-52.7013245,394,261,61
10010191,47.5322617,-52.7010442,892,323,23
10010291,47.57004,-52.7009,0,0,0
10010289,47.57141,-52.70023,0,0,0
10010285,47.5832183,-52.6995828,469,239,44
10010273,47.6006838,-52.6984875,855,283,28
10010190,47.472353,-52.697991,0,0,0
10010274,47.6018197,-52.6978362,344,117,51
10010288,47.5755249,-52.6978207,33,0,19
10010275,47.6005037,-52.6968299,232,93,43
10010279,47.5915368,-52.6954916,983,437,33
10010276,47.5993086,-52.6954808,329,131,28
10010278,47.5958782,-52.6934253,251,107,27
10010354,47.6165839,-52.6934037,27,14,47
10010277,47.5975113,-52.6914148,515,194,37
10010293,47.5778754,-52.6910827,58,0,40
10010292,47.5722183,-52.6899332,1112,523,28
10010353,47.6356972,-52.6896838,1387,471,32
10010283,47.5873992,-52.6884621,531,296,41
10010281,47.5983891,-52.6880528,307,113,52
10010280,47.5958439,-52.6878177,374,129,18
10010282,47.5999645,-52.6874407,637,226,22
10010286,47.5797909,-52.6872042,446,280,32
10010355,47.6210282,-52.6777189,197,72,39