i need create convex hull 4 polygons shapefile file. don't create using spatialpolygonsdataframe object, want use shapefile object, possible?
my code:
#packages require(rgdal) require(maptools) #------------------------------------------------------------------------------- #create 4 polygons sr <- spatialpolygons(list( polygons(list(polygon(cbind(c(180114, 180553, 181127, 181477, 181294, 181007, 180409, 180162, 180114), c(332349, 332057, 332342, 333250, 333558, 333676, 332618, 332413, 332349)))),'1'), polygons(list(polygon(cbind(c(180042, 180545, 180553, 180314, 179955, 179142, 179437, 179524, 179979, 180042), c(332373, 332026, 331426, 330889, 330683, 331133, 331623, 332152, 332357, 332373)))),'2'), polygons(list(polygon(cbind(c(179110, 179907, 180433, 180712, 180752, 180329, 179875, 179668, 179572, 179269, 178879, 178600, 178544, 179046, 179110), c(331086, 330620, 330494, 330265, 330075, 330233, 330336, 330004, 329783, 329665, 329720, 329933, 330478, 331062, 331086)))),'3'), polygons(list(polygon(cbind(c(180304, 180403,179632,179420,180304), c(332791, 333204, 333635, 333058, 332791)))),'4'))) plot(sr) #convert in polygon spatial srdf=spatialpolygonsdataframe(sr, data.frame(row.names=c('1','2','3','4'), pids=1:4)) srdf@data #create shapefile writeogr(srdf, getwd(), 'poly', 'esri shapefile') #read shapefile contorno_line_x <- readshapelines ("poly.shp") #plot plot(contorno_line_x) #try create convex hull df.data = as.data.frame(contorno_line_x) ch <- chull(df.data) lines(ch, col="red") ## doesn't work
here approach:
library(dismo) library(rgdal) sr <- spatialpolygons(list( polygons(list(polygon(cbind(c(180114, 180553, 181127, 181477, 181294, 181007, 180409, 180162, 180114), c(332349, 332057, 332342, 333250, 333558, 333676, 332618, 332413, 332349)))),'1'), polygons(list(polygon(cbind(c(180042, 180545, 180553, 180314, 179955, 179142, 179437, 179524, 179979, 180042), c(332373, 332026, 331426, 330889, 330683, 331133, 331623, 332152, 332357, 332373)))),'2'), polygons(list(polygon(cbind(c(179110, 179907, 180433, 180712, 180752, 180329, 179875, 179668, 179572, 179269, 178879, 178600, 178544, 179046, 179110), c(331086, 330620, 330494, 330265, 330075, 330233, 330336, 330004, 329783, 329665, 329720, 329933, 330478, 331062, 331086)))),'3'), polygons(list(polygon(cbind(c(180304, 180403,179632,179420,180304), c(332791, 333204, 333635, 333058, 332791)))),'4'))) srdf=spatialpolygonsdataframe(sr, data.frame(row.names=c('1','2','3','4'), pids=1:4)) shapefile(srdf, 'poly.shp') contorno <- shapefile("poly.shp") g <- geom(contorno) ids <- unique(g[,1]) hulls <- list() (i in ids) { d <- g[g[,1] == i, ] hulls[[i]] <- polygons(convhull(d[, c('x', 'y')])) } h <- do.call(bind, hulls) plot(h, col='red') plot(contorno, add=true, border='blue', lwd=3) 
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