p1 = st_point(c(7,52))
p2 = st_point(c(-30,20))
sfc = st_sfc(p1, p2, crs = "+init=epsg:4326")
st_transform(sfc, "+init=epsg:3857")
st_transform(st_sf(a=2:1, geom=sfc), "+init=epsg:3857")
st_transform(structure(p1, proj4string = "+init=epsg:4326"), "+init=epsg:3857")
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