CODEWITHSUNDEEP
rgeospatialdistance
bsauce
bsauce

Reputation: 672

Why does distHaversine return NaN for some pairs of coordinates?

I am trying to calculate the distance between all possible pairs of coordinates in a list of coordinates. However, I am surprisingly getting NaN for some pairs of coordinates that you should definitely be able to calculate the distance between.

My coordinates are in decimal longitude and latitude. I am using the distHaversine function from the geodist package in R.

Here is a sample of a pair of coordinates for which distHaversine returns NaN. I tried this code with many other pairs of coordinates and it works correctly.

# Create long, lat matrix with two sets of coordinates
coord_list <- matrix(c(2.5, -177.5, 5.5, -5.5), ncol=2)
coord_list

# Create a matrix with the distance between each pair of points (zero on the diagonals)
dist <- apply(coord_list, 1, 
              FUN=function(X) {
                distHaversine(X, coord_list)
              })
dist
#    [,1] [,2]
#[1,]    0  NaN
#[2,]  NaN    0

In case it's relevant, I need these distances for an inverse distance weighting matrix for spatially weighted regressions. However, I'd rather figure out why distHaversine is occasionally returning NaN than calculate the matrix differently (which I know how to do).

Thanks for your help!

Upvotes: 1

Views: 758

Answers (1)

Robert Hijmans
Robert Hijmans

Reputation: 47156

Thanks for reporting. This was fixed in geosphere 1.5-7.

I would use the very precise geosphere::distGeo function in stead of geopshere::distHaversine (which is more for historical interest)

To get the distance for all points to all points, you can use the distm function

coords <- matrix(c(2.5, -177.5, 5.5, -5.5, 0, 0), ncol=2)

library(geosphere)
distm(coords)

#           [,1]     [,2]       [,3]
#[1,]        0.0 19395754   693590.1
#[2,] 19395754.2        0 19703549.9
#[3,]   693590.1 19703550        0.0

Or the pointDistance function in the raster package (and the same algorithm as distGeo):

library(raster)
pointDistance(coords, lonlat=TRUE)

#           [,1]     [,2] [,3]
#[1,]        0.0       NA   NA
#[2,] 19395754.2        0   NA
#[3,]   693590.1 19703550    0

Upvotes: 0

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