CODEWITHSUNDEEP
rterra
Sara
Sara

Reputation: 525

How to generate a SpatVector from SpatExtent in R terra?

Does anybody know if there is a built-in function in R terra to generate a SpatVector polygon from an ext object, please?

library(terra)
# A SpatExtent object
ext1 <- ext(c(-74.5, -72.5, 9.5,  12.0))

How I manually created the coordinates of the polygon vertices

box_coords <- rbind(
   c(ext1[1], ext1[3]),
   c(ext1[2], ext1[3]),
   c(ext1[2], ext1[4]),
   c(ext1[1], ext1[4]),
   c(ext1[1], ext1[3])
)
box_coords
#      [,1] [,2]
#[1,] -74.5  9.5
#[2,] -72.5  9.5
#[3,] -72.5 12.0
#[4,] -74.5 12.0
#[5,] -74.5  9.5

How I convert the coordinate into a SpatVector

box1 <- vect(box_coords, type = "lines")

The way I'd like it to be, but that doesn't work

box1 <- vect(ext1)

Upvotes: 3

Views: 1287

Answers (1)

Robert Hijmans
Robert Hijmans

Reputation: 47536

You can use as.polygons

library(terra)
e <- ext(-74.5, -72.5, 9.5, 12.0)
p <- as.polygons(e, crs="")
# or 
p <- as.polygons(e, crs="+proj=longlat")

You can also use as.points and as.lines

To get a polygon for the extent of SpatRaster or SpatVector x you can do

x <- rast()
p <- as.polygons(x, extent=TRUE)

The latter has the advantage that the coordinate reference system is not lost, or is less convulted than the alternative

p <- as.polygons(ext(x), extent=TRUE, crs=crs(x))

I have now added this path as well (terra 1.7-6) .

ve <- vect(e, crs="+proj=longlat")

And, to get a numeric vector (not a SpatVector) you can do

as.vector(e)

Upvotes: 4

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