In R, how do I run st_convex_hull function on point sf object?

Question

I'm trying to get a convex hull of point features in R.

library(tmap)
library(sf)
nc <- st_centroid(st_read(system.file("shape/nc.shp", package="sf")))
qtm(nc)

ch <- st_convex_hull(nc) 
qtm(ch)

identical(nc, ch)

I'd expect the st_convex_hull to contain polygon with convex hull. However it returns points that are not identical. How can I get the polygon instead?

score 23 · Accepted Answer · answered Aug 07 '18 at 05:37

23

You need to union the points into MULTIPOINTS

library(tmap)
library(sf)
nc <- st_centroid(st_read(system.file("shape/nc.shp", package="sf")))
qtm(nc)

ch <- st_convex_hull(st_union(nc)) 
qtm(ch)

answered Aug 07 '18 at 05:37

TimSalabim

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Can this be applied to grouped data where an hull is generated for each group? – B. Davis Feb 22 '19 at 21:11
I don't see why it shouldn't be. – TimSalabim Feb 23 '19 at 08:46

In R, how do I run st_convex_hull function on point sf object?

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