问题
Given a data frame with latitudes and longitudes I want to add a column that simply contains the count of other points (of the same data frame) that are within a certain radius e.g. within 10 km of that specific point.
Example data:
set.seed(1)
radius<-10
lat<-runif(10,-90,90)
long<-runif(10,-180,180)
id<-1:10
dat<-cbind(id,lat,long)
id lat long
[1,] 1 -42.20844 -105.8491530
[2,] 2 -23.01770 -116.4395691
[3,] 3 13.11361 67.3282248
[4,] 4 73.47740 -41.7226614
[5,] 5 -53.69725 97.1429112
[6,] 6 71.71014 -0.8282728
[7,] 7 80.04155 78.3426630
[8,] 8 28.94360 177.0861941
[9,] 9 23.24053 -43.1873354
[10,] 10 -78.87847 99.8802797
Now given the radius variable I want a new column say "X" that for each point only contains the number of other points that are within "radius". I do not care about which points these are.
While this R - Finding closest neighboring point and number of neighbors within a given radius, coordinates lat-long topic and answer get close it does not solve the specific question of the simple count. This question is different as I need the counts of all points within the radius and not the points
回答1:
Try this:
library(geosphere)
cbind(dat, X=rowSums(distm (dat[,3:2],
fun = distHaversine) / 1000 <= 10000)) # number of points within distance 10000 km
id lat long X
[1,] 1 -42.20844 -105.8491530 5
[2,] 2 -23.01770 -116.4395691 5
[3,] 3 13.11361 67.3282248 5
[4,] 4 73.47740 -41.7226614 6
[5,] 5 -53.69725 97.1429112 4
[6,] 6 71.71014 -0.8282728 6
[7,] 7 80.04155 78.3426630 6
[8,] 8 28.94360 177.0861941 5
[9,] 9 23.24053 -43.1873354 6
[10,] 10 -78.87847 99.8802797 4
来源：https://stackoverflow.com/questions/40874731/calculating-number-of-points-within-a-certain-radius