Hi,
I am struggling to extract the polygon vertices from a list of an object class
"Polygons", specifically the slot "coords".
I have a point, and i "draw" a buffer around with gBuffer, i am "extracting"
the polygon form the SpatialPolygons class and i end up with a list of 1 one
object Polygons class that seems to have slots, but if i try to extract them i
get an error.
So here it goes after i load the respective libraries: sp, maptools, rgdal,
rgeos
pt1 <- data.frame(x=217680.2, y = 3817555)
coordinates(pt1) <- c("x", "y")
crs = "+proj=utm +zone=11 +datum=NAD83 +units=m +no_defs +ellps=GRS80
+towgs84=0,0,0"
proj4string(pt1) <- CRS(crs)
pt1.cpoly <- gBuffer(pt1, width = 100, byid = TRUE)
pt1.cpoly
class : SpatialPolygons
features : 1
extent : 217580.2, 217780.2, 3817455, 3817655 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=utm +zone=11 +datum=NAD83 +units=m +no_defs +ellps=GRS80
+towgs84=0,0,0
pt1.poly <- pt1.cpoly@polygons
pt1.poly
[[1]]
An object of class "Polygons"
Slot "Polygons":
[[1]]
An object of class "Polygon"
Slot "labpt":
[1] 217680.2 3817554.7
Slot "area":
[1] 30901.7
Slot "hole":
[1] FALSE
Slot "ringDir":
[1] 1
Slot "coords":
x y
[1,] 217780.2 3817555
[2,] 217775.3 3817524
[3,] 217761.1 3817496
[4,] 217739.0 3817474
Etc. …..
pt1.crd <- pt1.poly[[1]]@coords
Error: no slot of name "coords" for this object of class "Polygons"
So my question is: How do i access the "coords" slot i clearly see when i print
pt1.poly on the screen?
Thanks for any help,
Monica
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