R: Create SpatVector objects

vect {terra} | R Documentation

## Create SpatVector objects

### Description

Create a SpatVector

### Usage

    ## 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 (see`link{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

    ### 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)

[Package terra version 1.4-7 Index]