vect: Create SpatVector objects

Description Usage Arguments Value See Also Examples

Description

Create a SpatVector

Usage

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## S4 method for signature 'character'
vect(x, layer="", query="", extent=NULL, filter=NULL, crs="")

## 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="")

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

Arguments

x

character. A filename; or a "Well Known Text" string; or a data.frame (only to make a SpatVector of points); or a "geom" matrix to make a SpatVector of any supported geometry (see examples and geom); or a spatial vector data object defined in the sf or sp packages

layer

character. layer name to select a layer from a file (database) with multiple layers

query

character. An 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

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

the coordinate reference system in one of the following formats: WKT/WKT2, <authority>:<code>, or PROJ-string notation (seelink{crs})

geom

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)

Value

SpatVector

See Also

geom

Examples

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### 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")
v

## 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. 11, 2021, 9:09 a.m.