R convert sf object back to SpatialPolygonsDataFrame

Question

How do I convert an sf object back to a SpatialPolygonsDataFrame?

I am running R 3.4.0 and sf version 0.4.1. The sf documentation mentions an as_Spatial function, but this isn't available in my install (for some reason).

The coersion method is avalible at sf 0.4-1, what hapens when you try to call the function? — Jeffrey Evans, May 04 '17 at 02:39
@Jeffrey Evans, Kazuhito's answer below replicates the problem (and provides a partial solition) — Simon, May 04 '17 at 08:04

andschar · Accepted Answer · 2017-08-15T10:46:27.177

63

I used

 as(nc, 'Spatial')

as part 2 of the vignette by Edzer Pebesma indicated (Scroll to the bottom of the page).

edited Aug 15 '17 at 10:46

answered May 04 '17 at 16:31

andschar

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saw it. However I figured this out only recently and I felt the urge to put it into a proper answer when seeing this question ;) – andschar May 05 '17 at 07:46
And it is important the accepted answer will not be overlooked by future readers. – Kazuhito May 06 '17 at 02:05
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For this to truly work like a SPDF, I needed to do something like: tmp <-as(nc, 'Spatial'), then tmpid <- sapply(slot(tmp, "polygons"), function(x) slot(x, "ID")) then row.names(tmp) <- tmpid – Simon May 15 '17 at 11:50
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what does 'truly work like a SPDF' mean? I see no disadvantage created by the conversion. – andschar May 15 '17 at 14:16

score 14 · Answer 2 · answered May 04 '17 at 04:24

14

I had to use sf:::as_Spatial() as workaround.

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

# sf -> sp
nc_sp <- as_Spatial(nc$geom)      # Error: could not find function "as_Spatial"

nc_sp <- sf:::as_Spatial(nc$geom) # This works

library(sp)
plot(nc_sp)

answered May 04 '17 at 04:24

Kazuhito

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Is there a way to keep the dataframe intact? – Simon May 04 '17 at 08:03
Running as(sf, "Spatial") by @mdsumner , I confirm it produces SpatialPolygonsDataFrame, which is better for your requirement. It seems as_Spatial() takes sfc (ie geometry) only. – Kazuhito May 04 '17 at 08:08
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This function is a method and is ment to be call using as(). It is not exported as a function object which is why, to call it directly, you need ":::". – Jeffrey Evans May 04 '17 at 17:29
it seems the as() function is no longer in the sf package – mattador Aug 16 '22 at 14:10
as_Spatial(nc) will keep the dataframe intact! – M-- May 11 '23 at 18:59

R convert sf object back to SpatialPolygonsDataFrame

2 Answers2