Creating empty SpatialPoints or SpatialPointsDataFrame in R?

Question

I have been trying to create an empty SpatialPoints in R but have not found the way yet.

I have tried with this formula:

SpatialPoints(as.matrix(data.table(x = numeric(), y = numeric())))

But it didn't work. The closest thing I have found on the internet is Creating empty Polygons or SpatialPolygons in R? but that is for polygons and apparently it does not work the same way.

I have sp version 1.2.7

• Spacedman: You should think about why you want to create this. If its to put in a for loop to incrementally add points to, you might be better off using an apply-type operation and then combining the results in the end - this is usually faster than growing a vector from an empty object.

Answer 1

Create a SpatialPoints object with one row in it, and then drop it with [-1,]:

> zero = SpatialPoints(data.frame(x = 0, y = 0))[-1,]
> zero
SpatialPoints:
 x y
Coordinate Reference System (CRS) arguments: NA 

Quick test to see what this thing is:

> length(zero)
[1] 0
> class(zero)
[1] "SpatialPoints"
attr(,"package")
[1] "sp"

• Andre Silva: [temp_comment] by chance I found a duplicate account of yours (gis.stackexchange.com/users/3537/spacedman?tab=profile). Is it on purpose? If you are interested, you can merge them (gis.stackexchange.com/help/merging-accounts).

Answer 2

Maybe there is a shorter way ...

new("SpatialPoints", 
 coords = structure(numeric(0), .Dim = c(0L, 2L), 
 .Dimnames = list(NULL, c("coords.x1", "coords.x2"))), 
 bbox = structure(c(1, 1, 1, 1), .Dim = c(2L, 2L), 
 .Dimnames = list(c("coords.x1", "coords.x2"),
 c("min", "max"))),
 proj4string = new("CRS", projargs = NA_character_)) 
# SpatialPoints:
# coords.x1 coords.x2
# Coordinate Reference System (CRS) arguments: NA