g_query: Obtain information about WKB/WKT geometries

In gdalraster: Bindings to 'GDAL'

Obtain information about WKB/WKT geometries

Description

These functions return information about WKB/WKT geometries. The input geometries may be given as a single raw vector of WKB, a list of WKB raw vectors, or a character vector containing one or more WKT strings.

Usage

g_is_empty(geom, quiet = FALSE)

g_is_valid(geom, quiet = FALSE)

g_is_3D(geom, quiet = FALSE)

g_is_measured(geom, quiet = FALSE)

g_name(geom, quiet = FALSE)

g_summary(geom, quiet = FALSE)

Arguments

geom	Either a raw vector of WKB or list of raw vectors, or a character vector containing one or more WKT strings.
quiet	Logical value, TRUE to suppress warnings. Defaults to FALSE.

Details

g_is_empty() tests whether a geometry has no points. Returns a logical vector of the same length as the number of input geometries containing TRUE for the corresponding geometries that are empty or FALSE for non-empty geometries.

g_is_valid() tests whether a geometry is valid. Returns a logical vector analogous to the above for g_is_empty().

g_is_3D() checks whether a geometry has Z coordinates. Returns a logical vector analogous to the above for g_is_empty().

g_is_measured() checks whether a geometry is measured (has M values). Returns a logical vector analogous to the above for g_is_empty().

g_name() returns the WKT type names of the input geometries in a character vector of the same length as the number of input geometries.

g_summary() returns text summaries of WKB/WKT geometries in a character vector of the same length as the number of input geometries. Requires GDAL >= 3.7.

Examples

g1 <- "POLYGON ((0 0, 10 10, 10 0, 0 0))"
g2 <- "POLYGON ((5 1, 9 5, 9 1, 5 1))"
g_difference(g2, g1) |> g_is_empty()

g1 <- "POLYGON ((0 0, 10 10, 10 0, 0 0))"
g2 <- "POLYGON ((0 0, 10 10, 10 0))"
g3 <- "POLYGON ((0 0, 10 10, 10 0, 0 1))"
g_is_valid(c(g1, g2, g3))

g_is_3D(g1)
g_is_measured(g1)

pt_xyz <- g_create("POINT", c(1, 9, 100))
g_is_3D(pt_xyz)
g_is_measured(pt_xyz)

pt_xyzm <- g_create("POINT", c(1, 9, 100, 2000))
g_is_3D(pt_xyzm)
g_is_measured(pt_xyzm)

f <- system.file("extdata/ynp_fires_1984_2022.gpkg", package = "gdalraster")
lyr <- new(GDALVector, f, "mtbs_perims")

feat <- lyr$getNextFeature()
g_name(feat$geom)

# g_summary() requires GDAL >= 3.7
if (gdal_version_num() >= gdal_compute_version(3, 7, 0)) {
  feat <- lyr$getNextFeature()
  g_summary(feat$geom) |> print()

  feat_set <- lyr$fetch(5)
  g_summary(feat_set$geom) |> print()
}

lyr$close()

gdalraster documentation built on June 8, 2025, 12:37 p.m.