Class "gpc.poly"
A class for representing polygons composed of multiple contours, some of which may be holes.
Objects can be created by calls of the form new("gpc.poly",
...) or by reading in from a file using read.polyfile.
Object of class “list”. Actually,
pts is a list of lists with length equal to the number of
contours in the "gpc.poly" object. Each element of
pts is a list of length 3 with names x, y,
and hole. x and y are vectors containing the
x and y coordinates, respectively, while hole is a logical
indicating whether or not the contour is a hole.
signature(x = "gpc.poly"): ...
signature(x = "gpc.poly", y = "gpc.poly"): ...
signature(object = "gpc.poly"): ...
signature(from = "matrix", to = "gpc.poly"): ...
signature(from = "data.frame", to = "gpc.poly"): ...
signature(from = "numeric", to = "gpc.poly"): ...
signature(from = "list", to = "gpc.poly"): ...
signature(from = "SpatialPolygons", to = "gpc.poly"): ...
signature(from = "gpc.poly", to = "matrix"): ...
signature(from = "gpc.poly", to = "numeric"): ...
signature(from = "gpc.poly", to = "SpatialPolygons"): ...
signature(x = "gpc.poly"): ...
signature(object = "gpc.poly"): ...
signature(x = "gpc.poly", y = "gpc.poly"): ...
signature(x = "gpc.poly"): The argument
poly.args can be used to pass a list of additional
arguments to be passed to the underlying polygon call.
signature(x = "gpc.poly"): ...
signature(x = "gpc.poly", y = "gpc.poly"): ...
signature(object = "gpc.poly"): Scale x and y
coordinates by amount xscale and yscale. By default
xscale equals yscale.
signature(x = "gpc.poly", y = "gpc.poly"): ...
signature(x = "gpc.poly", y = "gpc.poly"): ...
signature(x = "gpc.poly"): ...
signature(x = "gpc.poly"): ...
The class "gpc.poly.nohole" is identical to
"gpc.poly" except the hole flag for each contour of a
"gpc.poly.nohole" object is always FALSE.
Roger D. Peng
## Make some random polygons
set.seed(100)
a <- cbind(rnorm(100), rnorm(100))
a <- a[chull(a), ]
## Convert `a' from matrix to "gpc.poly"
a <- as(a, "gpc.poly")
b <- cbind(rnorm(100), rnorm(100))
b <- as(b[chull(b), ], "gpc.poly")
## More complex polygons with an intersection
p1 <- read.polyfile(system.file("poly-ex-gpc/ex-poly1.txt", package = "rgeos"))
p2 <- read.polyfile(system.file("poly-ex-gpc/ex-poly2.txt", package = "rgeos"))
## Plot both polygons and highlight their intersection in red
plot(append.poly(p1, p2))
plot(intersect(p1, p2), poly.args = list(col = 2), add = TRUE)
## Highlight the difference p1 \ p2 in green
plot(setdiff(p1, p2), poly.args = list(col = 3), add = TRUE)
## Highlight the difference p2 \ p1 in blue
plot(setdiff(p2, p1), poly.args = list(col = 4), add = TRUE)
## Plot the union of the two polygons
plot(union(p1, p2))
## Take the non-intersect portions and create a new polygon
## combining the two contours
p.comb <- append.poly(setdiff(p1, p2), setdiff(p2, p1))
plot(p.comb, poly.args = list(col = 2, border = 0))
## Coerce from a matrix
x <-
structure(c(0.0934073560027759, 0.192713393476752, 0.410062456627342,
0.470020818875781, 0.41380985426787, 0.271408743927828, 0.100902151283831,
0.0465648854961832, 0.63981588032221, 0.772382048331416,
0.753739930955121, 0.637744533947066, 0.455466052934407,
0.335327963176065, 0.399539700805524,
0.600460299194476), .Dim = c(8, 2))
y <-
structure(c(0.404441360166551, 0.338861901457321, 0.301387925052047,
0.404441360166551, 0.531852879944483, 0.60117973629424, 0.625537820957668,
0.179976985040276, 0.341542002301496, 0.445109321058688,
0.610817031070196, 0.596317606444189, 0.459608745684695,
0.215189873417722), .Dim = c(7, 2))
x1 <- as(x, "gpc.poly")
y1 <- as(y, "gpc.poly")
plot(append.poly(x1, y1))
plot(intersect(x1, y1), poly.args = list(col = 2), add = TRUE)
## Show the triangulation
#plot(append.poly(x1, y1))
#triangles <- triangulate(append.poly(x1,y1))
#for (i in 0:(nrow(triangles)/3 - 1))
# polygon(triangles[3*i + 1:3,], col="lightblue")Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.