I have produced a SpatialPoints object (named v3) in R from the function gIntersection (package rgeos). The SpatialPoints object v3 has the following structure and is represented by red points on the image below.
> summary(v3)
Object of class SpatialPoints
Coordinates:
min max
x 310440.5 310680.5
y 4996427.5 4997297.5
Is projected: TRUE
proj4string :
[+proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0
+units=m +no_defs]
Number of points: 32
From the SpatialPoints object v3, how can I convert the red points into 3 spatial lines as in the image below ?
The SpatialPoints object v3 has only spatial coordinates x and y.
Update
I used the function gIntersection with two objects of class spatialPolygons (squares in the images) and I almost get the desired result (i.e., to draw boundaries between polygons that have different values). But the function gIntersection creates a object of class SpatialCollections with 1 feature. So, How can I convert objects of class SpatialCollections into objects of class SpatialLines ? From the reproducible example, I would like to get only the lines in red (and not the points).
Here the reproducible example:
r <- raster(ncols=90, nrows=50, resolution = 30)
projection(r) <- CRS("+proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs")
values(r) <- sample(1:3, ncell(r), replace=TRUE)
plot(r)
p1 <- rasterToPolygons(r, fun=function(x){x==1})
plot(p1,add=T)
p1 <- as(p1,"SpatialPolygons")
p2 <- rasterToPolygons(r, fun=function(x){x==3})
plot(p2,add=T)
p2 <- as(p2,"SpatialPolygons")
p3 <- gIntersection(p1,p2,byid=T)
plot(p3,add=T,col="red",lwd=3)
> p3
class : SpatialCollections
features : 1
extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=tmerc +lat_0=0 +lon_0=-73.5 +k=0.9999 +x_0=304800 +y_0=0 +ellps=GRS80 +datum=NAD83 +units=m +no_defs +towgs84=0,0,0
