[R-sig-Geo] Mixing points and sf objects

[Roger Bivand]

On Thu, 3 Mar 2022, Patrick Giraudoux wrote:

> Dear listers,
>
> Just for curiosity, using one sf object (depts) and one classical
> data.frame with two columns bearing coordinates, I wonder why this
> sequence works (points and department limits are correctly drawn):
>
> plot(chbrut[,5:6],asp=1)
> plot(st_geometry(depts),add=TRUE)
>
> .. but not this one (points of chbrut are not projected - or projected
> somewhere else, and are not visible on the map)
>
> plot(st_geometry(depts),reset=FALSE)
> points(chbrut[,5:6],pch=19,col=cols)

Sorry, cannot reproduce:

library(sf)
nc <- st_read(system.file("gpkg/nc.gpkg", package="sf"))
nc_xy <- st_transform(nc, "EPSG:32019")
set.seed(1)
pts <- as.data.frame(st_coordinates(st_sample(nc_xy, 100)))

plot(pts, asp=1)
plot(st_geometry(nc_xy), add=TRUE)

and

plot(st_geometry(nc_xy))
points(pts)

seem the same. reset= is irrelevant if the plot method for sfc objects is 
used, I think it applies to sf objects only, when multiple maps may be 
displayed with keys.

Hope this helps,

Roger


>
> Best,
>
> Patrick
>
> 	[[alternative HTML version deleted]]
>
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-- 
Roger Bivand
Emeritus Professor
Department of Economics, Norwegian School of Economics,
Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway.
e-mail: Roger.Bivand using nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en