vect: Create SpatVector objects

In terra: Spatial Data Analysis

Create SpatVector objects

Description

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

A filename can be for a shapefile or any spatial file format.

You can use a data.frame 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 signature 'character'
vect(x, layer="", query="", extent=NULL, filter=NULL, 
		crs="", proxy=FALSE, what="", opts=NULL)

## S4 method for signature 'matrix'
vect(x, type="points", atts=NULL, crs="")

## S4 method for signature 'data.frame'
vect(x, geom=c("lon", "lat"), crs="", keepgeom=FALSE)

## S4 method for signature 'list'
vect(x, type="points", crs="")

## S4 method for signature 'SpatExtent'
vect(x, crs="")

## S4 method for signature 'SpatVectorCollection'
vect(x)

## S4 method for signature 'sf'
vect(x)

Arguments

x	character. A filename; or a "Well Known Text" string; SpatExtent, data.frame (to make a SpatVector of points); a "geom" matrix to make a SpatVector of any supported geometry (see examples and geom); a spatial vector data object defined in the sf or sp packages; or a list with matrices with coordinates
layer	character. layer name to select a layer from a file (database) with multiple layers
query	character. A query to subset the dataset in the OGR-SQL dialect
extent	Spat* object. The extent of the object is used as a spatial filter to select the geometries to read. Ignored if filter is not NULL
filter	SpatVector. Used as a spatial filter to select geometries to read (the convex hull is used for lines or points). It is guaranteed that all features that overlap with the extent of filter will be returned. It can happen that additional geometries are returned
type	character. Geometry type. Must be "points", "lines", or "polygons"
atts	data.frame with the attributes. The number of rows must match the number of geometrical elements
crs	character. The coordinate reference system in one of the following formats: WKT/WKT2, <authority>:<code>, or PROJ-string notation (see crs)
proxy	logical. If TRUE a SpatVectorProxy is returned
what	character indicating what to read. Either "" for geometries and attributes, or "geoms" to only read the geometries, "attributes" to only read the attributes (that are returned as a data.frame)
opts	character. GDAL dataset open options
geom	character. The field name(s) with the geometry data. Either two names for x and y coordinates of points, or a single name for a single column with WKT geometries
keepgeom	logical. If TRUE the geom variable(s) is (are) also included in the attributes

Value

SpatVector

See Also

geom

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)

terra documentation built on Oct. 14, 2024, 5:07 p.m.