Sorry for my previous answer, I didn't get the question fully. I'm afraid I still don't get the question fully, but functions that might help are sf::st_line_merge (creates a LINESTRING from line pieces) and sf::st_polygonize (creates a polygon from a LINESTRING that forms a closed ring)
On 11/5/18 5:35 PM, Patrick Giraudoux wrote: > > Apologize to answer to myself: the way described below would work only > if there are no concave "peninsula" towards north or south inside the > polygon. Even thinking about an alternate solution, e.g. the Traveling > Salesman Problem (TSP), ie. the shortest route linking all points, one > could get wrong since points of a narrowpeninsula could have points > closest to the opposite border than from the next point on the border... > > Suppose we are stuck, and should redraw polygons by hand > > > Le 05/11/2018 à 14:02, Patrick Giraudoux a écrit : >> >> Dear listers, >> >> There is an interesting post here: >> https://stackoverflow.com/questions/6989100/sort-points-in-clockwise-order >> dealing on the issue. However, I would like to know if a function has >> been already developped in a R package. >> >> I am coping with a young colleague's shapefile where borders of >> polygons have been drawn as lines quite inconsistently. To change this >> SpatialLinesDataFrame into a SpatialPoints object is easy. The idea is >> to select the points bordering each polygon (delete the others), >> define the point set as a Polygon, then rebuild step by step a >> SpatialPolygonsDataFrame with all its (~25) polygons. It would be much >> quicker than to redraw one by one the 5160 data points (two times on >> borders shared by two polygons). >> >> The problem is that the points must be reordered clockwise (the way >> lines making the borders is all except clockwise) before making them >> a polygon. >> >> Any function already developped for that ? >> >> Cheers, >> >> Patrick >> >> >> > > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-Geo mailing list > [email protected] > https://stat.ethz.ch/mailman/listinfo/r-sig-geo > -- Edzer Pebesma Institute for Geoinformatics Heisenbergstrasse 2, 48151 Muenster, Germany Phone: +49 251 8333081
pEpkey.asc
Description: application/pgp-keys
_______________________________________________ R-sig-Geo mailing list [email protected] https://stat.ethz.ch/mailman/listinfo/r-sig-geo
