Create SpatVector objects

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; 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 class 'character'
vect(x, layer="", query="", dialect="", extent=NULL, filter=NULL, 
    crs="", proxy=FALSE, what="", opts=NULL)

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

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

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

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

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

# S4 method for class '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 either matrices with coordinates, or raw "Well Known Binary" (WKB) blobs
layer: character. layer name to select a layer from a file (database) with multiple layers
query: character. A query to subset the dataset
dialect: character. The SQL dialect to use (if any). For example: "SQLite". "" refers to the default 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". Ignored if x is a WKB list
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. For example "ENCODING=LATIN1"
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), e.g. spatial coordinates, is (are) also included in the attributes table

Value

SpatVector

Examples

### SpatVector from file
f <- system.file("ex/lux.shp", package="terra")
f
#> [1] "/home/runner/work/_temp/Library/terra/ex/lux.shp"
v <- vect(f)
v
#>  class       : SpatVector 
#>  geometry    : polygons 
#>  dimensions  : 12, 6  (geometries, attributes)
#>  extent      : 5.74414, 6.528252, 49.44781, 50.18162  (xmin, xmax, ymin, ymax)
#>  source      : lux.shp
#>  coord. ref. : lon/lat WGS 84 (EPSG:4326) 
#>  names       :  ID_1   NAME_1  ID_2   NAME_2  AREA       POP
#>  type        : <num>    <chr> <num>    <chr> <num>     <num>
#>  values      :     1 Diekirch     1 Clervaux   312 1.808e+04
#>                    1 Diekirch     2 Diekirch   218 3.254e+04
#>                    1 Diekirch     3  Redange   259 1.866e+04

## 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
#>  class       : SpatVector 
#>  geometry    : polygons 
#>  dimensions  : 3, 0  (geometries, attributes)
#>  extent      : -180, 160, -60, 60  (xmin, xmax, ymin, ymax)
#>  coord. ref. :  

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)

Usage

Arguments

See also

Value

Examples