# Lon-Lat to Simple Features (sfg and sfc) in R

How can I convert lon-lat points to simple features (sfg), and then put them in a simple feature collection (sfc)?

Here is a MWE that doesn't work but is the closest I have gotten to.

``````library(data.table)
library(sf)
# The DT data.table is the data I have (but 10,000s of rows, each row is a point)
DT <- data.table(
longitude=c(27.472918, -90.476303, 34.679950, -65.691146, 4.533465),
latitude=c(63.293001, 54.239631, -2.855123, -13.795272, 48.603949),
crs="+proj=longlat +datum=WGS84")
DT[, rowid:=1:.N]
# The following two rows do not work
DT[, place.sfg:=st_point(x=c(longitude, latitude), dim="XY"), by=rowid]
places.sfc <- st_sfc(DT[, place.sfg], crs=DT[, crs])
# This should result in five points, which it doesn't
plot(places.sfc)
``````

I'm trying to learn Simple Features (which is why I do not want to use library sp), and later need to run st_buffer on the sfc.

Maybe better to create the sfc directly, without an sfg per point?

I use data.table for speed-reasons (10,000s of thousands of points that are also analysed without geographical aspects).

I think I need an sfc of sfg-points, and not a MULTIPOINT-sfg.

Have you tried st_as_sf() which converts object (sp, dataframe, ...) to an sf object?

``````library(data.table)
library(sf)
# your data (removed crs column)
DT <- data.table(
longitude=c(27.472918, -90.476303, 34.679950, -65.691146, 4.533465),
latitude=c(63.293001, 54.239631, -2.855123, -13.795272, 48.603949))
# st_as_sf() ######
# sf version 0.2-7
DT_sf = st_as_sf(DT, coords = c("longitude", "latitude"),
crs = 4326, relation_to_geometry = "field")
# sf version 0.3-4, 0.4-0
DT_sf = st_as_sf(DT, coords = c("longitude", "latitude"),
crs = 4326, agr = "constant")
plot(DT_sf)
``````

As commented by @cengel, it would be important to keep up with rapid development of this package.

• I guess this has been updated in sf. Running this example, I get an error "Error in st_sf(x, ..., agr = agr, sf_column_name = sf_column_name) : no simple features geometry column present". Commented May 24, 2021 at 4:02