Set the right crs on sf object to plot coordinate points

Question

I'm trying to define the right CRS for my sf object. I want to plot points atop the following layer (country: the Netherlands):

Simple feature collection with 380 features and 3 fields
geometry type:  MULTIPOLYGON
dimension:      XY
bbox:           xmin: 13565.4 ymin: 306846.2 xmax: 278026.1 ymax: 619232.6
epsg (SRID):    NA
proj4string:    +proj=sterea +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.9999079 +x_0=155000 +y_0=463000 +ellps=bessel +units=m +no_defs

output:

This layer has the correct projection.

But the POINT layer doesn't have the correct CRS project presumably because it has no proj4string?

Simple feature collection with 566 features and 5 fields
geometry type:  POINT
dimension:      XY
bbox:           xmin: 3.5837 ymin: 50.86487 xmax: 7.120998 ymax: 53.44835
epsg (SRID):    NA
proj4string:    NA

How do I set the same projection as the previous map so I can plot the coordinates points on it?

Answer 1

You can use st_crs.

As it says in the examples:

st_crs(x) <- value 

In your case it would probably be

st_crs(points) <- st_crs(polygons)

Note: the points should be registered in the same coordinate system, of course. If not, you would have to find out the correct coordinate system for them and then use st_transform to put them into the same coordinate system as the polygons.

Answer 2

In addition, there is the function st_set_crs(), which can be used in a pipe. For example,

points %>% st_set_crs(st_crs(polygons))