SpatialLinesDataFrame: how to calculate the min. distance between a point and a line

Question

I have a SpatialLinesDataFrame with streets and I have a list of GPS coordinates. What I need to do is to get out the 10 closest street names for each individual GPS coordinate.

Answer 1

You could use rgeos::gDistance() with byid=TRUE to get a matrix of distances from each point to each line. From there, it's relatively easy to extract the ids of the 10 lines nearest to each point:

library(sp)
library(rgeos)

## Create a SpatialPoints and a SpatialLines object
example("SpatialPoints-class", ask=FALSE, echo=FALSE)
example("SpatialLines-class", ask=FALSE, echo=FALSE)

## Compute the matrix of distances between them.
(m <- gDistance(S, Sl, byid=TRUE))
#          1   2        3        4        5
# a 0.000000 0.0 2.757716 1.414214 2.757716
# b 1.788854 0.5 3.640055 1.000000 3.605551

## And then use it to extract the ids of the 10 (or in this case 1) lines
## closest to each point.
## apply(m, 2, function(X) rownames(m)[order(X)][1:10]) ## Finds 10 closest
apply(m, 2, function(X) rownames(m)[order(X)][1])       ## Finds single closest
#   1   2   3   4   5 
# "a" "a" "a" "b" "a"