vapour_geom_summary: Summary of available geometry

In vapour: Access to the 'Geospatial Data Abstraction Library' ('GDAL')

Summary of available geometry

Description

Read properties of geometry from a source, optionally after SQL execution.

Usage

vapour_geom_summary(
  dsource,
  layer = 0L,
  sql = "",
  limit_n = NULL,
  skip_n = 0,
  extent = NA
)

Arguments

dsource	data source name (path to file, connection string, URL)
layer	integer of layer to work with, defaults to the first (0) or the name of the layer
sql	if not empty this is executed against the data source (layer will be ignored)
limit_n	an arbitrary limit to the number of features scanned
skip_n	an arbitrary number of features to skip
extent	apply an arbitrary extent, only when 'sql' used (must be 'ex = c(xmin, xmax, ymin, ymax)' but sp bbox, sf bbox, and raster extent also accepted)

Details

Use limit_n to arbitrarily limit the number of features queried.

Value

list containing the following

• FID the feature id value (an integer, usually sequential)

• valid_geometry logical value if a non-empty geometry is available

• type integer value of geometry type from GDAL enumeration

• ⁠xmin, xmax, ymin, ymax⁠ numeric values of the extent (bounding box) of each geometry

Examples

file <- "list_locality_postcode_meander_valley.tab"
mvfile <- system.file(file.path("extdata/tab", file), package="vapour")
vapour_geom_summary(mvfile, limit_n = 3L)

gsum <- vapour_geom_summary(mvfile)
plot(NA, xlim = range(c(gsum$xmin, gsum$xmax), na.rm = TRUE),
         ylim = range(c(gsum$ymin, gsum$ymax), na.rm = TRUE))
rect(gsum$xmin, gsum$ymin, gsum$xmax, gsum$ymax)
text(gsum$xmin, gsum$ymin, labels = gsum$FID)

vapour documentation built on June 22, 2024, 10:01 a.m.