Re: [R-sig-Geo] Identifying adjacent polygons within larger polygon groupings
Thank you so much! -Original Message- From: R-sig-Geo On Behalf Of Edzer Pebesma Sent: Thursday, April 1, 2021 3:27 PM To: r-sig-geo@r-project.org Subject: Re: [R-sig-Geo] Identifying adjacent polygons within larger polygon groupings On 01/04/2021 17:01, Sean Trende wrote: > Hello, > > I am using sf for the project below, but am open to non-sf solutions. > > Given an sf data.frame of polygons sorted into n contiguous groups (e.g., a > column in the df identifies each polygon as a member of group (1, . . ., n), > where within each group all polygons are neighbors), is there a simple way to > identify all polygons in, say, Group 5 that are neighbors to polygons in, > say, Group 8 (assuming groups 5 and 8 are neighbors)? > > E.g., if I have an sf data.frame of U.S. counties with a column that > identifies the state in which each county is located, is there a way to > identify all counties on the border between, say, Kansas and Nebraska? Yes, look into using st_intersects (or st_touches) with x the counties of Kansas and y the counties of Nebraska. What you get back is a list of length length(x), with integer vectors, the i-th vector containing the indexes of Nebraska counties touching/intersecting county i of Kansas. > > Thank you so much, > > Sean > > ___ > R-sig-Geo mailing list > R-sig-Geo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Edzer Pebesma Institute for Geoinformatics Heisenbergstrasse 2, 48151 Muenster, Germany Phone: +49 251 8333081 ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
Re: [R-sig-Geo] Identifying adjacent polygons within larger polygon groupings
On 01/04/2021 17:01, Sean Trende wrote: Hello, I am using sf for the project below, but am open to non-sf solutions. Given an sf data.frame of polygons sorted into n contiguous groups (e.g., a column in the df identifies each polygon as a member of group (1, . . ., n), where within each group all polygons are neighbors), is there a simple way to identify all polygons in, say, Group 5 that are neighbors to polygons in, say, Group 8 (assuming groups 5 and 8 are neighbors)? E.g., if I have an sf data.frame of U.S. counties with a column that identifies the state in which each county is located, is there a way to identify all counties on the border between, say, Kansas and Nebraska? Yes, look into using st_intersects (or st_touches) with x the counties of Kansas and y the counties of Nebraska. What you get back is a list of length length(x), with integer vectors, the i-th vector containing the indexes of Nebraska counties touching/intersecting county i of Kansas. Thank you so much, Sean ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo -- Edzer Pebesma Institute for Geoinformatics Heisenbergstrasse 2, 48151 Muenster, Germany Phone: +49 251 8333081 ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
[R-sig-Geo] Identifying adjacent polygons within larger polygon groupings
Hello, I am using sf for the project below, but am open to non-sf solutions. Given an sf data.frame of polygons sorted into n contiguous groups (e.g., a column in the df identifies each polygon as a member of group (1, . . ., n), where within each group all polygons are neighbors), is there a simple way to identify all polygons in, say, Group 5 that are neighbors to polygons in, say, Group 8 (assuming groups 5 and 8 are neighbors)? E.g., if I have an sf data.frame of U.S. counties with a column that identifies the state in which each county is located, is there a way to identify all counties on the border between, say, Kansas and Nebraska? Thank you so much, Sean ___ R-sig-Geo mailing list R-sig-Geo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-geo
