Re: [R-sig-Geo] Combine two polygons
Dear Ben,
Thank you for your help. I will try this out. What I want to do is combine
the polygons of Cyprus and Northern Cyprus into one single polygon
eliminating the border. For the GADM, I am only interested in the
country-level shapefile. Thanks again!
Best regards,
Milu
On Fri, Apr 28, 2023 at 4:41 PM Ben Tupper wrote:
> Hi Milu,
>
> If you want to combine just a few of the thousands of features in
> world then you will have to manage them individually. Essentially
> extract the subset to be combined, do the combination steps, and then
> add them back to the world. I am very not familiar with GADM and I
> only have version 4.1, but all of the attributes appear to be
> character type, which raises the question about what you want
> aggregate() to do - it can't take the mean of a character attribute.
> In the example below I show how you might take just the first value of
> each attribute. While this combining is possible, it doesn't mean
> that you will have "correct" attributes with your new single feature.
> I guess you'll have to figure out what you really want to do with
> that.
>
> ### start here
> library(sf)
> library(dplyr)
> # a function called by aggregate() for each attribute
> first_item = function(x){
> x[[1]]
> }
> # read in the database downlaoded from https://gadm.org/data.html
> world = read_sf("~/Downloads/gadm_410.gpkg")
> # find the Cypriot features (we'll use this twice)
> ix = grepl("Cyp", world$NAME_0, fixed = TRUE)
> # pull them out of world
> Cyp_features = dplyr::filter(world, ix)
> # aggregate - which works for the geometry but is wrong in terms of
> handling the attributes
> Cyp_union = aggregate(Cyp_features,
> sf::st_union(Cyp_features),
> first_item)
> # bind the world (less Cypriot features) with the combined Cypriot
> aggregation
> new_world = dplyr::bind_rows(dplyr::filter(world, !ix), Cyp_union)
> ### end here
>
>
> Does that help?
>
> Ben
>
>
> On Fri, Apr 28, 2023 at 8:28 AM Roger Bivand wrote:
> >
> > Briefly, is sf::aggregate() what you are looking for? Or
> terra::aggregate() if you read with terra::vect()?
> >
> > ---
> > Roger Bivand
> > Emeritus Professor
> > Department of Economics
> > Norwegian School of Economics, Bergen, Norway
> >
> >
> > Fra: Miluji Sb
> > Sendt: fredag 28. april 2023, 14:18
> > Til: Roger Bivand
> > Kopi: Michael Sumner ; R-sig-geo mailing list <
> [email protected]>
> > Emne: Re: [R-sig-Geo] Combine two polygons
> >
> > Thank you for your replies. I think I am misunderstanding something. I
> have read the shapefile using sf. I would like to combine polygons for
> Cyprus and Northern Cyprus only within the world shapefile and keep all the
> other polygons as they are.
> >
> > world <- sf::st_read(dsn = "~/gadm36_levels_shp", layer = "gadm36_0")
> >
> > Is something like the following correct? I was thinking of generating a
> group variable which is unique to all the countries except Cyprus and
> Northern Cyprus. I a probably making this too complicated.
> >
> > world %>%
> > group_by(group) %>%
> > summarise(geometry = sf::st_union(geometry)) %>%
> > ungroup()
> >
> > Thank you again.
> >
> > Best regards,
> >
> > Milu
> >
> > On Fri, Apr 28, 2023 at 8:56 AM Roger Bivand <mailto:[email protected]>> wrote:
> > On Fri, 28 Apr 2023, Michael Sumner wrote:
> >
> > > fwiw, a method with geodata/terra
> > >
> > > cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(),
> version =
> > > "3.6")
> > >
> > > terra::aggregate(cyp)
> > >
> >
> > and as per
> > https://github.com/r-spatial/evolution/blob/main/pkgapi_230305_refs.csv.
> >
> > > see ?terra::writeVector to write it out
> > >
> > > (rgdal is very old and you should abandon it, it will be removed from
> > > support by the end of this year)
> >
> > Thank you! Yes, sp will by default switch to using sf in place of rgdal
> > for creating "CRS" objects, and under sp::spTransform in June, and all
> > three retiring packages rgdal, rgeos, and maptools will be gone by
> October
> > 2023. An sp release will appear in May with a transition guide.
> >
> > It seems that terra does not have an object corresponding to sp's "CRS"
> or
> > sf's "crs". As far as I can see, one
Re: [R-sig-Geo] Combine two polygons
Hi Milu,
If you want to combine just a few of the thousands of features in
world then you will have to manage them individually. Essentially
extract the subset to be combined, do the combination steps, and then
add them back to the world. I am very not familiar with GADM and I
only have version 4.1, but all of the attributes appear to be
character type, which raises the question about what you want
aggregate() to do - it can't take the mean of a character attribute.
In the example below I show how you might take just the first value of
each attribute. While this combining is possible, it doesn't mean
that you will have "correct" attributes with your new single feature.
I guess you'll have to figure out what you really want to do with
that.
### start here
library(sf)
library(dplyr)
# a function called by aggregate() for each attribute
first_item = function(x){
x[[1]]
}
# read in the database downlaoded from https://gadm.org/data.html
world = read_sf("~/Downloads/gadm_410.gpkg")
# find the Cypriot features (we'll use this twice)
ix = grepl("Cyp", world$NAME_0, fixed = TRUE)
# pull them out of world
Cyp_features = dplyr::filter(world, ix)
# aggregate - which works for the geometry but is wrong in terms of
handling the attributes
Cyp_union = aggregate(Cyp_features,
sf::st_union(Cyp_features),
first_item)
# bind the world (less Cypriot features) with the combined Cypriot aggregation
new_world = dplyr::bind_rows(dplyr::filter(world, !ix), Cyp_union)
### end here
Does that help?
Ben
On Fri, Apr 28, 2023 at 8:28 AM Roger Bivand wrote:
>
> Briefly, is sf::aggregate() what you are looking for? Or terra::aggregate()
> if you read with terra::vect()?
>
> ---
> Roger Bivand
> Emeritus Professor
> Department of Economics
> Norwegian School of Economics, Bergen, Norway
>
>
> Fra: Miluji Sb
> Sendt: fredag 28. april 2023, 14:18
> Til: Roger Bivand
> Kopi: Michael Sumner ; R-sig-geo mailing list
>
> Emne: Re: [R-sig-Geo] Combine two polygons
>
> Thank you for your replies. I think I am misunderstanding something. I have
> read the shapefile using sf. I would like to combine polygons for Cyprus and
> Northern Cyprus only within the world shapefile and keep all the other
> polygons as they are.
>
> world <- sf::st_read(dsn = "~/gadm36_levels_shp", layer = "gadm36_0")
>
> Is something like the following correct? I was thinking of generating a group
> variable which is unique to all the countries except Cyprus and Northern
> Cyprus. I a probably making this too complicated.
>
> world %>%
> group_by(group) %>%
> summarise(geometry = sf::st_union(geometry)) %>%
> ungroup()
>
> Thank you again.
>
> Best regards,
>
> Milu
>
> On Fri, Apr 28, 2023 at 8:56 AM Roger Bivand
> mailto:[email protected]>> wrote:
> On Fri, 28 Apr 2023, Michael Sumner wrote:
>
> > fwiw, a method with geodata/terra
> >
> > cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(), version =
> > "3.6")
> >
> > terra::aggregate(cyp)
> >
>
> and as per
> https://github.com/r-spatial/evolution/blob/main/pkgapi_230305_refs.csv.
>
> > see ?terra::writeVector to write it out
> >
> > (rgdal is very old and you should abandon it, it will be removed from
> > support by the end of this year)
>
> Thank you! Yes, sp will by default switch to using sf in place of rgdal
> for creating "CRS" objects, and under sp::spTransform in June, and all
> three retiring packages rgdal, rgeos, and maptools will be gone by October
> 2023. An sp release will appear in May with a transition guide.
>
> It seems that terra does not have an object corresponding to sp's "CRS" or
> sf's "crs". As far as I can see, one needs to create an empty
> SpatVector/SpatRaster object and assign a CRS, coerce to "Spatial", and
> extract its slot. If this makes sense, sp could use terra (and
> raster, needed for coercion) rather than sf where workflows did not
> otherwise use sf. Very grateful for input here or
> https://github.com/r-spatial/evolution/issues.
>
> Roger
>
> >
> >
> > (just as an aside, we can't hit the geodata vector urls directly with gdal
> > as we can with the rasters, as they are in an R specific format)
> >
> > Cheers, Mike
> >
> >
> > On Fri, Apr 28, 2023 at 10:52 AM Ben Tupper
> > mailto:[email protected]>> wrote:
> >
> >> Hi,
> >>
> >> You might try st_union() from the sf package
> >> https://r-spatial.github.io/sf/a
Re: [R-sig-Geo] Combine two polygons
Briefly, is sf::aggregate() what you are looking for? Or terra::aggregate() if you read with terra::vect()? --- Roger Bivand Emeritus Professor Department of Economics Norwegian School of Economics, Bergen, Norway Fra: Miluji Sb Sendt: fredag 28. april 2023, 14:18 Til: Roger Bivand Kopi: Michael Sumner ; R-sig-geo mailing list Emne: Re: [R-sig-Geo] Combine two polygons Thank you for your replies. I think I am misunderstanding something. I have read the shapefile using sf. I would like to combine polygons for Cyprus and Northern Cyprus only within the world shapefile and keep all the other polygons as they are. world <- sf::st_read(dsn = "~/gadm36_levels_shp", layer = "gadm36_0") Is something like the following correct? I was thinking of generating a group variable which is unique to all the countries except Cyprus and Northern Cyprus. I a probably making this too complicated. world %>% group_by(group) %>% summarise(geometry = sf::st_union(geometry)) %>% ungroup() Thank you again. Best regards, Milu On Fri, Apr 28, 2023 at 8:56 AM Roger Bivand mailto:[email protected]>> wrote: On Fri, 28 Apr 2023, Michael Sumner wrote: > fwiw, a method with geodata/terra > > cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(), version = > "3.6") > > terra::aggregate(cyp) > and as per https://github.com/r-spatial/evolution/blob/main/pkgapi_230305_refs.csv. > see ?terra::writeVector to write it out > > (rgdal is very old and you should abandon it, it will be removed from > support by the end of this year) Thank you! Yes, sp will by default switch to using sf in place of rgdal for creating "CRS" objects, and under sp::spTransform in June, and all three retiring packages rgdal, rgeos, and maptools will be gone by October 2023. An sp release will appear in May with a transition guide. It seems that terra does not have an object corresponding to sp's "CRS" or sf's "crs". As far as I can see, one needs to create an empty SpatVector/SpatRaster object and assign a CRS, coerce to "Spatial", and extract its slot. If this makes sense, sp could use terra (and raster, needed for coercion) rather than sf where workflows did not otherwise use sf. Very grateful for input here or https://github.com/r-spatial/evolution/issues. Roger > > > (just as an aside, we can't hit the geodata vector urls directly with gdal > as we can with the rasters, as they are in an R specific format) > > Cheers, Mike > > > On Fri, Apr 28, 2023 at 10:52 AM Ben Tupper > mailto:[email protected]>> wrote: > >> Hi, >> >> You might try st_union() from the sf package >> https://r-spatial.github.io/sf/articles/sf3.html#geometrical-operations >> >> >> >> On Thu, Apr 27, 2023 at 5:37 PM Miluji Sb >> mailto:[email protected]>> wrote: >> >>> Dear all, >>> >>> I am using the country-level shapefile from GADM. I would like to merge >>> Cyprus and North Cyprus into one polygon. Is this possible? I am using >>> rgdal to read the shapefile, subset, and then rewrite it. Any help will >> be >>> highly appreciated. >>> >>> ## >>> world <- readOGR("~/gadm36_levels_shp", layer = "gadm36_0") >>> >>> Best regards, >>> >>> Milu >>> >>> [[alternative HTML version deleted]] >>> >>> ___ >>> R-sig-Geo mailing list >>> [email protected]<mailto:[email protected]> >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >>> >> >> [[alternative HTML version deleted]] >> >> ___ >> R-sig-Geo mailing list >> [email protected]<mailto:[email protected]> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo >> > > > -- Roger Bivand Emeritus Professor Department of Economics, Norwegian School of Economics, Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway. e-mail: [email protected]<mailto:[email protected]> https://orcid.org/-0003-2392-6140 https://scholar.google.no/citations?user=AWeghB0J&hl=en___ R-sig-Geo mailing list [email protected]<mailto:[email protected]> https://stat.ethz.ch/mailman/listinfo/r-sig-geo [[alternative HTML version deleted]] ___ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Combine two polygons
Thank you for your replies. I think I am misunderstanding something. I have
read the shapefile using sf. I would like to combine polygons for Cyprus
and Northern Cyprus only within the world shapefile and keep all the other
polygons as they are.
world <- sf::st_read(dsn = "~/gadm36_levels_shp", layer = "gadm36_0")
Is something like the following correct? I was thinking of generating a
group variable which is unique to all the countries except Cyprus and
Northern Cyprus. I a probably making this too complicated.
world %>%
group_by(group) %>%
summarise(geometry = sf::st_union(geometry)) %>%
ungroup()
Thank you again.
Best regards,
Milu
On Fri, Apr 28, 2023 at 8:56 AM Roger Bivand wrote:
> On Fri, 28 Apr 2023, Michael Sumner wrote:
>
> > fwiw, a method with geodata/terra
> >
> > cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(),
> version =
> > "3.6")
> >
> > terra::aggregate(cyp)
> >
>
> and as per
> https://github.com/r-spatial/evolution/blob/main/pkgapi_230305_refs.csv.
>
> > see ?terra::writeVector to write it out
> >
> > (rgdal is very old and you should abandon it, it will be removed from
> > support by the end of this year)
>
> Thank you! Yes, sp will by default switch to using sf in place of rgdal
> for creating "CRS" objects, and under sp::spTransform in June, and all
> three retiring packages rgdal, rgeos, and maptools will be gone by October
> 2023. An sp release will appear in May with a transition guide.
>
> It seems that terra does not have an object corresponding to sp's "CRS" or
> sf's "crs". As far as I can see, one needs to create an empty
> SpatVector/SpatRaster object and assign a CRS, coerce to "Spatial", and
> extract its slot. If this makes sense, sp could use terra (and
> raster, needed for coercion) rather than sf where workflows did not
> otherwise use sf. Very grateful for input here or
> https://github.com/r-spatial/evolution/issues.
>
> Roger
>
> >
> >
> > (just as an aside, we can't hit the geodata vector urls directly with
> gdal
> > as we can with the rasters, as they are in an R specific format)
> >
> > Cheers, Mike
> >
> >
> > On Fri, Apr 28, 2023 at 10:52 AM Ben Tupper wrote:
> >
> >> Hi,
> >>
> >> You might try st_union() from the sf package
> >> https://r-spatial.github.io/sf/articles/sf3.html#geometrical-operations
> >>
> >>
> >>
> >> On Thu, Apr 27, 2023 at 5:37 PM Miluji Sb wrote:
> >>
> >>> Dear all,
> >>>
> >>> I am using the country-level shapefile from GADM. I would like to merge
> >>> Cyprus and North Cyprus into one polygon. Is this possible? I am using
> >>> rgdal to read the shapefile, subset, and then rewrite it. Any help will
> >> be
> >>> highly appreciated.
> >>>
> >>> ##
> >>> world <- readOGR("~/gadm36_levels_shp", layer = "gadm36_0")
> >>>
> >>> Best regards,
> >>>
> >>> Milu
> >>>
> >>> [[alternative HTML version deleted]]
> >>>
> >>> ___
> >>> R-sig-Geo mailing list
> >>> [email protected]
> >>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>>
> >>
> >> [[alternative HTML version deleted]]
> >>
> >> ___
> >> R-sig-Geo mailing list
> >> [email protected]
> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>
> >
> >
> >
>
> --
> Roger Bivand
> Emeritus Professor
> Department of Economics, Norwegian School of Economics,
> Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway.
> e-mail: [email protected]
> https://orcid.org/-0003-2392-6140
> https://scholar.google.no/citations?user=AWeghB0J&hl=en
> ___
> R-sig-Geo mailing list
> [email protected]
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
[[alternative HTML version deleted]]
___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Combine two polygons
On Fri, 28 Apr 2023, Michael Sumner wrote:
fwiw, a method with geodata/terra
cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(), version =
"3.6")
terra::aggregate(cyp)
and as per
https://github.com/r-spatial/evolution/blob/main/pkgapi_230305_refs.csv.
see ?terra::writeVector to write it out
(rgdal is very old and you should abandon it, it will be removed from
support by the end of this year)
Thank you! Yes, sp will by default switch to using sf in place of rgdal
for creating "CRS" objects, and under sp::spTransform in June, and all
three retiring packages rgdal, rgeos, and maptools will be gone by October
2023. An sp release will appear in May with a transition guide.
It seems that terra does not have an object corresponding to sp's "CRS" or
sf's "crs". As far as I can see, one needs to create an empty
SpatVector/SpatRaster object and assign a CRS, coerce to "Spatial", and
extract its slot. If this makes sense, sp could use terra (and
raster, needed for coercion) rather than sf where workflows did not
otherwise use sf. Very grateful for input here or
https://github.com/r-spatial/evolution/issues.
Roger
(just as an aside, we can't hit the geodata vector urls directly with gdal
as we can with the rasters, as they are in an R specific format)
Cheers, Mike
On Fri, Apr 28, 2023 at 10:52 AM Ben Tupper wrote:
Hi,
You might try st_union() from the sf package
https://r-spatial.github.io/sf/articles/sf3.html#geometrical-operations
On Thu, Apr 27, 2023 at 5:37 PM Miluji Sb wrote:
Dear all,
I am using the country-level shapefile from GADM. I would like to merge
Cyprus and North Cyprus into one polygon. Is this possible? I am using
rgdal to read the shapefile, subset, and then rewrite it. Any help will
be
highly appreciated.
##
world <- readOGR("~/gadm36_levels_shp", layer = "gadm36_0")
Best regards,
Milu
[[alternative HTML version deleted]]
___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
[[alternative HTML version deleted]]
___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
--
Roger Bivand
Emeritus Professor
Department of Economics, Norwegian School of Economics,
Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway.
e-mail: [email protected]
https://orcid.org/-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0J&hl=en___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Combine two polygons
fwiw, a method with geodata/terra
cyp <- geodata::gadm(country = c("CYP", "XNC"), path = tempdir(), version =
"3.6")
terra::aggregate(cyp)
see ?terra::writeVector to write it out
(rgdal is very old and you should abandon it, it will be removed from
support by the end of this year)
(just as an aside, we can't hit the geodata vector urls directly with gdal
as we can with the rasters, as they are in an R specific format)
Cheers, Mike
On Fri, Apr 28, 2023 at 10:52 AM Ben Tupper wrote:
> Hi,
>
> You might try st_union() from the sf package
> https://r-spatial.github.io/sf/articles/sf3.html#geometrical-operations
>
>
>
> On Thu, Apr 27, 2023 at 5:37 PM Miluji Sb wrote:
>
> > Dear all,
> >
> > I am using the country-level shapefile from GADM. I would like to merge
> > Cyprus and North Cyprus into one polygon. Is this possible? I am using
> > rgdal to read the shapefile, subset, and then rewrite it. Any help will
> be
> > highly appreciated.
> >
> > ##
> > world <- readOGR("~/gadm36_levels_shp", layer = "gadm36_0")
> >
> > Best regards,
> >
> > Milu
> >
> > [[alternative HTML version deleted]]
> >
> > ___
> > R-sig-Geo mailing list
> > [email protected]
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
>
> [[alternative HTML version deleted]]
>
> ___
> R-sig-Geo mailing list
> [email protected]
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
--
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: [email protected]
[[alternative HTML version deleted]]
___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Combine two polygons
Hi,
You might try st_union() from the sf package
https://r-spatial.github.io/sf/articles/sf3.html#geometrical-operations
On Thu, Apr 27, 2023 at 5:37 PM Miluji Sb wrote:
> Dear all,
>
> I am using the country-level shapefile from GADM. I would like to merge
> Cyprus and North Cyprus into one polygon. Is this possible? I am using
> rgdal to read the shapefile, subset, and then rewrite it. Any help will be
> highly appreciated.
>
> ##
> world <- readOGR("~/gadm36_levels_shp", layer = "gadm36_0")
>
> Best regards,
>
> Milu
>
> [[alternative HTML version deleted]]
>
> ___
> R-sig-Geo mailing list
> [email protected]
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
[[alternative HTML version deleted]]
___
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
