Package index • GDAL7

The package

GDAL7 GDAL7-package: GDAL7: Modern GDAL Bindings for R Using S7

Classes

Every GDAL handle reaches R as one of these S7 classes. Their accessors are properties rather than get_/set_ functions, so a dataset’s size, projection and geotransform are read with @ and set the same way where GDAL allows it.

GDALMajorObject(): GDAL MajorObject class
GDALDataset(): GDAL Dataset class
GDALDriver(): GDALDriver class
GDALRasterBand(): GDALRasterBand class
GDALLayer(): GDAL layer class
GDALGroup(): GDALGroup class
GDALMDArray(): GDALMDArray class

Open and close a dataset

Opening is where a source is told what its own metadata does not say, and closing is where a written dataset is actually finished. A dataset closes itself when R garbage collects it, so gdal_close() is for closing it sooner rather than for avoiding a leak.

gdal_open(): Open a GDAL dataset
gdal_close(): Close a GDAL dataset
gdal_flush(): Write out everything held in memory
gdal_info(): Summarise a dataset in one call
mark_suppress_on_close(): MarkSuppressOnClose
get_thread_safe_dataset() is_thread_safe(): A view of a dataset that several threads may read at once
get_close_reports_progress(): GetCloseReportsProgress

Drivers

What this build of GDAL can read and write, and what a given driver will accept. Asking the library beats trusting a version number, because a driver is only present if it was compiled in.

gdal_drivers(): Every driver this GDAL has
gdal_get_driver_count(): Get the number of registered GDAL drivers
gdal_get_driver(): Get a driver by index
gdal_get_driver_by_name(): Get a driver by name
get_driver(): Get the driver that opened a dataset
driver_options(): What a driver will accept
has_open_option(): Check if driver has an open option
validate_creation_options(): Check creation options against a driver
test_capability(): Test driver capability

Raster I/O

read_raster() is one call onto GDALRasterIOEx: a fractional source window, an output size chosen independently of it, a resampling algorithm, and the values read straight into the R vector of the requested type. Overviews are reached explicitly when a band’s own pyramid is wanted. warp_raster() reprojects onto a grid with GDAL’s warp API, into bands or a nativeRaster.

read_raster(): Read a window of raster data
warp_raster(): Warp a dataset onto a grid
advise_read(): Tell GDAL what is about to be read
get_raster_band(): Get a raster band from a dataset
get_overview(): Get one overview of a band
flush_cache(): FlushCache
clear_statistics(): ClearStatistics

Vector

Features come back over GDAL’s own Arrow stream rather than feature by feature, so a layer read is a columnar transfer. The filters and the SQL are set on the layer before the stream is asked for, and transactions wrap edits on drivers that support them.

read_vector(): Read a vector layer into a data frame
get_layer(): Get a layer from a dataset
feature_count(): Count the features of a layer
get_extent(): The bounding box of a layer
set_filter(): Restrict which features a layer returns
reset_reading(): ResetReading
arrow_stream(): The Arrow stream of a layer
release_arrow_stream(): Give an Arrow stream back to its layer
execute_sql(): Run an SQL statement against a dataset
abort_sql(): AbortSQL
start_transaction(): StartTransaction
commit_transaction(): CommitTransaction
rollback_transaction(): RollbackTransaction
get_field_domain_names(): GetFieldDomainNames
delete_field_domain(): DeleteFieldDomain
get_relationship_names(): GetRelationshipNames
delete_relationship(): DeleteRelationship

Multidimensional

GDAL’s multidimensional model, for the sources that have more than two dimensions: netCDF, Zarr, HDF5. read_mdarray() returns dim in the order the values arrive in, which is the reverse of GDAL’s own dimension order; the array’s dimensions property still reports GDAL’s.

get_root_group(): Get root group from a multidimensional dataset
open_group(): Open a subgroup from a group
open_mdarray(): Open an array from a group
read_mdarray(): Read from a multidimensional array
as_altarr(): A GDAL array or band as a lazy R array
mdarray_info(): Everything about an array in one call
get_view(): Take a view of an array
as_classic_dataset(): See a two-dimensional slice of an array as an ordinary raster
as_mdarray(): AsMDArray

Algorithms and pipelines

GDAL’s own algorithm registry, the C API behind the gdal command line. A pipeline is named and its arguments passed as a list, so anything the installed GDAL registers is callable without a wrapper being written for it here. Not every build has it: ask gdal_has_algorithms() first.

gdal_has_algorithms(): Whether this GDAL has algorithms to run
gdal_algorithms(): List GDAL's algorithms
gdal_algorithm_info(): Describe one of GDAL's algorithms
gdal_run(): Run one of GDAL's algorithms

Creating and writing

The write side. A dataset is created empty and filled, or copied from an existing one in a single driver call, and creation options are validated against the driver rather than discovered by the write failing.

gdal_create(): Create a new raster dataset
gdal_create_copy(): Copy a dataset, in another format or with other options
gdal_delete(): Delete a dataset
write_raster(): Write a raster window
write_vector(): Write a data frame to a vector dataset
add_band(): AddBand
create_mask_band(): CreateMaskBand

Metadata

Metadata on any major object, in GDAL’s domains. The same six functions serve a dataset, a band, a layer, a group and an array.

get_metadata_list(): GetMetadata_List
get_metadata_dict(): GetMetadata_Dict
get_metadata_item(): GetMetadataItem
set_metadata(): SetMetadata
set_metadata_2(): SetMetadata (overload 2)
set_metadata_item(): SetMetadataItem

Coordinates and extents

Moving between pixel space, projected space and another coordinate reference system. transform_extent() walks the edges of a box rather than transforming its four corners, which is the difference between a correct box and a wrong one wherever an edge is not monotonic.

crs_to_wkt(): A coordinate reference system as WKT
pixel_to_xy() xy_to_pixel(): Convert between pixel and georeferenced coordinates
transform_extent(): Move an extent between coordinate reference systems

File systems

GDAL’s virtual file system, which is how a path into a zip, an S3 bucket or an HTTP range request is read like a local file. These work on any /vsi… path as well as on ordinary ones.

vfs_list() vfs_stat() vfs_exists(): GDAL's virtual file systems
vfs_read_file() vfs_write_file(): Read and write bytes over a GDAL virtual file system
vfs_unlink() vfs_mkdir() vfs_rmdir() vfs_rename() vfs_copy(): Change a GDAL virtual file system

Configuration and capabilities

What this build can do, and how to change how it behaves. GDAL’s configuration options are process-global, so with_gdal_config() sets them for one expression and restores them afterwards.

gdal_config() gdal_config_options() with_gdal_config(): GDAL's configuration options
gdal7_capabilities(): What this build of GDAL7 can reach
gdal_release(): The GDAL library GDAL7 is running against
gdal_constants(): GDAL's integer constants
gdal_data_types() gdal_color_interpretations(): GDAL enum tables
gdal_string_constants(): GDAL's string constants