Create a GVector from a GRASS vector

Create a GVector from a vector existing in the current GRASS session.

Usage

makeGVector(
  src,
  table = NULL,
  build = TRUE,
  extensive = FALSE,
  cats = NULL,
  fail = TRUE
)

Arguments

src

Character: The name of the vector in GRASS.

table

A data.table, data.frame, GVector with a table, or character. This can be data.table(NULL) or data.frame(NULL) if there is no table associated with the vector. If a character, this is interpreted as the name of the table in GRASS.

build

Logical: If TRUE (default), build topology using GRASS tool v.build.

extensive

Logical: If TRUE, do extensive topological checks using v.build. The default is FALSE.

cats

NULL (default) or an integer vector: Values of the "cats" (categories) of the vector in GRASS. This is useful only for speeding up the GVector creation process when the "cats" have already been ascertained. For most users, this will be better left as NULL.

fail

Logical: If TRUE (default), and the vector either has a 0 east-west or north-south extent, then exit the function with an error. If fail is FALSE, then display a warning and return NULL.

Value

A GVector (or NULL if fail is TRUE and the GVector would be invalid).

See also

makeGRaster()

Examples

if (grassStarted()) {

# Setup
library(sf)
library(terra)

# Example data
madElev <- fastData("madElev") # integer raster
madCover <- fastData("madCover") # categorical raster
madCoast4 <- fastData("madCoast4") # polygons vector
madRivers <- fastData("madRivers") # lines vector
madDypsis <- fastData("madDypsis") # points vector

### Create GRasters from SpatRasters

# Create an integer raster:
elev <- fast(madElev)
elev

# Create a categorical raster:
cover <- fast(madCover)
madCover
levels(madCover) # category levels

# Create a GRaster from a file on disk:
rastFile <- system.file("extdata", "madForest2000.tif", package = "fasterRaster")
forest2000 <- fast(rastFile)
forest2000

# Create a 1's raster that spans the world:
ones <- fast(rastOrVect = "raster", crs = "epsg:4326")
ones

### Create GVectors

# Create a GVector from an sf vector:
coast4 <- fast(madCoast4)
coast4

# Create a GVector from a SpatVector:
madRivers <- vect(madRivers)
class(madRivers)
rivers <- fast(madRivers)
rivers

# Create a GVector from a vector on disk:
vectFile <- system.file("extdata/shapes", "madCoast.shp",
   package = "fasterRaster")
coast0 <- fast(vectFile)
coast0

# Import only Dypsis occurrences in a restricted area:
ant <- coast4[coast4$NAME_4 == "Antanambe"]
dypsisRestrict <- fast(madDypsis, extent = ant)
dypsis <- fast(madDypsis)

plot(coast4)
plot(ant, col = "gray80", add = TRUE)
plot(dypsis, add = TRUE)
plot(dypsisRestrict, col = "red", add = TRUE)

# Create a generic GVector that spans the world:
wallToWall <- fast(rastOrVect = "vector", crs = "epsg:4326") # WGS84
wallToWall

# Create a GVector from a numeric vector
pts <- c(-90.2, 38.6, -122.3, 37.9)
pts <- fast(pts, crs = "epsg:4326") # WGS84

# Create a GVector from a matrix (can also use data.frame or data.table):
mat <- matrix(c(-90.2, 38.6, -122.3, 37.9), ncol = 2, byrow = TRUE)
mat <- fast(mat, crs = "epsg:4326", keepgeom = TRUE) # WGS84

}