Fast points reprojection

In {sf} you can find the sf_project() function, which is used to reproject points by the PROJ library directly (bypassing GDAL), which is a faster alternative to st_transform().

Code

library("sf")

n = 500000
df = data.frame(x = rnorm(n), y = rnorm(n))
pts = st_as_sf(df, coords = c("x", "y"), crs = "EPSG:4326")

system.time({
  x = st_transform(pts, crs = "EPSG:3857")
})

##    user  system elapsed 
##    1.57    0.06    1.65

system.time({
  y = sf_project(from = "EPSG:4326", to = "EPSG:3857", pts = st_coordinates(pts))
  y = st_as_sf(as.data.frame(y), crs = "EPSG:3857", coords = 1:2)
})

##    user  system elapsed 
##    0.19    0.00    0.19

identical(x, y)

## [1] TRUE