terra (version 1.9-11)

vect: Create SpatVector objects

Description

Methods to create a SpatVector from a filename or other R object.

A filename can be for a Shapefile, GeoPackage, GeoJSON, Keyhole Markup Language (KML) or any other spatial vector file format.

You can use a data.frame to make a SpatVector of points. If the variables to be used are not specified with argument geom, the method looks for candidate variables. If variables are found and these appear to be longitude/latitude, the "+proj=longlat" crs is assigned unless another crs is specified.

You can also use a two-column matrix to make a SpatVector of points, or a "geom" matrix to make a SpatVector of any supported geometry (see examples and geom).

You can supply a list of SpatVectors to append them into a single SpatVector.

SpatVectors can also be created from "Well Known Text", and from spatial vector data objects defined in the sf or sp packages.

Usage

# S4 method for character
vect(x, layer="", query="", dialect="", extent=NULL, filter=NULL, 
		crs="", proxy=FALSE, what="", opts=NULL)
# S4 method for matrix
vect(x, type="points", atts=NULL, crs="")
# S4 method for data.frame
vect(x, geom=NULL, crs=NULL, keepgeom=FALSE, quiet=TRUE)
# S4 method for list
vect(x, type="points", crs="")
# S4 method for SpatExtent
vect(x, crs="")
# S4 method for SpatVectorCollection
vect(x)
# S4 method for sf
vect(x)

Value

SpatVector

See Also

geom, vector_layers

Examples

### SpatVector from file
f <- system.file("ex/lux.shp", package="terra")
f
v <- vect(f)
v

## subsetting (large) files
## with attribute query 
v <- vect(f, query="SELECT NAME_1, NAME_2, ID_2 FROM lux WHERE ID_2 < 4")

## with an extent
e <- ext(5.9, 6.3, 49.9, 50) 
v <- vect(f, extent=e)

## with polygons
p <- as.polygons(e)
v <- vect(f, filter=p)


### SpatVector from a geom matrix
x1 <- rbind(c(-180,-20), c(-140,55), c(10, 0), c(-140,-60))
x2 <- rbind(c(-10,0), c(140,60), c(160,0), c(140,-55))
x3 <- rbind(c(-125,0), c(0,60), c(40,5), c(15,-45))
hole <- rbind(c(80,0), c(105,13), c(120,2), c(105,-13))
z <- rbind(cbind(object=1, part=1, x1, hole=0), cbind(object=2, part=1, x3, hole=0),
			cbind(object=3, part=1, x2, hole=0), cbind(object=3, part=1, hole, hole=1))
colnames(z)[3:4] <- c('x', 'y')

p <- vect(z, "polygons")
p

z[z[, "hole"]==1, "object"] <- 4
lns <- vect(z[,1:4], "lines")
plot(p)
lines(lns, col="red", lwd=2)

### from wkt
v <- vect("POLYGON ((0 -5, 10 0, 10 -10, 0 -5))")

wkt <- c("MULTIPOLYGON ( ((40 40, 20 45, 45 30, 40 40)), 
((20 35, 10 30, 10 10, 30 5, 45 20, 20 35),(30 20, 20 15, 20 25, 30 20)))", 
"POLYGON ((0 -5, 10 0, 10 -10, 0 -5))")
w <- vect(wkt)

# combine two SpatVectors 
vw <- rbind(w, v)

# add a data.frame
d <- data.frame(id=1:2, name=c("a", "b"))
values(w) <- d

# add data.frame on creation, here from a geom matrix
g <- geom(w)
d <- data.frame(id=1:2, name=c("a", "b"))
m <- vect(g, "polygons", atts=d, crs="+proj=longlat +datum=WGS84")

### SpatVector from a data.frame
d$wkt <- wkt
x <- vect(d, geom="wkt")

d$wkt <- NULL
d$lon <- c(0,10)
d$lat <- c(0,10)
x <- vect(d, geom=c("lon", "lat"))

# SpatVector to sf
#sf::st_as_sf(x)