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# gdalraster

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## Overview

**gdalraster** is an R interface to the Raster and Vector
[APIs](https://gdal.org/en/stable/api/index.html) of the Geospatial Data
Abstraction Library ([GDAL](https://gdal.org/en/stable/)).

API bindings are implemented in the exposed C++ classes
[`GDALRaster`](https://firelab.github.io/gdalraster/reference/GDALRaster-class.html)
and
[`GDALVector`](https://firelab.github.io/gdalraster/reference/GDALVector-class.html),
along with several [stand-alone
functions](https://firelab.github.io/gdalraster/reference/index.html#stand-alone-functions).
Initial bindings are provided to the “gdal” command line interface (CLI)
algorithms added in GDAL 3.11. Bindings to the GDAL Virtual Systems
Interface ([VSI](https://gdal.org/en/stable/api/cpl.html#cpl-vsi-h)) are
also included to support file system operations on URLs, cloud storage
services, Zip/GZip/7z/RAR, and in-memory files, as well as regular file
systems. Calling signatures resemble the native C, C++ and Python APIs
provided by the GDAL project.

The package supports:

- [using GDAL’s new CLI
  algorithms](https://firelab.github.io/gdalraster/articles/use-gdal-cli-from-r.html)
  from R when built against GDAL \>= 3.11.3
- manual creation of uninitialized raster and vector datasets
- vector layer creation and schema management
- read/set parameters and metadata for raster bands and vector layers
- low-level I/O
- build/read/set color tables and raster attribute tables
- virtual raster (VRT) for virtual cropping, resampling, kernel
  filtering, mosaicing
- [raster
  utilities](https://firelab.github.io/gdalraster/reference/index.html#raster-utilities)
- GDAL multidimensional raster
  ([`mdim_as_classic()`](https://firelab.github.io/gdalraster/reference/mdim_as_classic.html),
  [`mdim_info()`](https://firelab.github.io/gdalraster/reference/mdim_info.html),
  [`mdim_translate()`](https://firelab.github.io/gdalraster/reference/mdim_translate.html))
- coordinate transformation
- spatial reference systems
- [geometry
  API](https://firelab.github.io/gdalraster/reference/index.html#geometry)
  operating on raw vectors of WKB or WKT strings
- [vector
  utilities](https://firelab.github.io/gdalraster/reference/index.html#vector-utilities)
- GDAL facilities for [vector
  geoprocessing](https://firelab.github.io/gdalraster/reference/ogr_proc.html)
- [dataset
  management](https://firelab.github.io/gdalraster/reference/index.html#general-data-management)
  (inspect/copy files/rename/delete)
- create/append to Seek-Optimized ZIP
  ([SOZip](https://github.com/sozip/sozip-spec))
- abstraction of [file system
  operations](https://firelab.github.io/gdalraster/reference/index.html#virtual-file-systems)
  on URLs, cloud storage, in-memory files, etc.
- Standard C binary file I/O through VSI (class
  [`VSIFile`](https://firelab.github.io/gdalraster/reference/VSIFile-class.html))

Additional functionality includes:

- class
  [`RunningStats`](https://firelab.github.io/gdalraster/reference/RunningStats-class.html)
  calculates mean and variance in one pass, and tracks the min, max,
  sum, and count (i.e., summary statistics on a data stream). The input
  data values are not stored in memory, so this class can be used to
  compute statistics for very large data streams.
- class
  [`CmbTable`](https://firelab.github.io/gdalraster/reference/CmbTable-class.html)
  identifies and counts unique combinations of integer values using a
  hash table.
- [`combine()`](https://firelab.github.io/gdalraster/reference/combine.html)
  overlays multiple rasters so that a unique ID is assigned to each
  unique combination of input values. Pixel counts for each unique
  combination are obtained, and combination IDs are optionally written
  to an output raster.
- [`calc()`](https://firelab.github.io/gdalraster/reference/calc.html)
  evaluates an R expression for each pixel in a raster layer or stack of
  layers. Individual pixel coordinates are available as variables in the
  R expression, as either x/y in the raster projected coordinate system
  or inverse projected longitude/latitude.
- plot raster data, vector layers and WKB/WKT geometries

**gdalraster** may be useful in applications that need scalable,
low-level I/O, or prefer a direct GDAL API. Comprehensive
[documentation](#documentation) is provided in the package and online.

## Installation

### From CRAN

Install the released version from CRAN with:

``` r
install.packages("gdalraster")
```

CRAN provides pre-compiled binary packages for Windows and macOS. These
do not require any separate installation of external libraries for GDAL.

### From conda-forge

[Conda-forge](https://github.com/conda-forge/r-gdalraster-feedstock)
provides pre-compiled binary packages that track CRAN releases, for the
following platforms:

[![Conda
Platforms](https://img.shields.io/conda/pn/conda-forge/r-gdalraster.svg)](https://anaconda.org/conda-forge/r-gdalraster)

To install **gdalraster** into a particular conda environment with
[conda](https://docs.conda.io/projects/conda/en/stable/), in the
activated environment:

    conda install --channel conda-forge r-gdalraster

### From R-universe

[R-universe](https://firelab.r-universe.dev/gdalraster) provides
pre-compiled binary packages for Windows and macOS that track the
development version of **gdalraster**. New packages are built usually
within ~1 hour of the most recent commit in branch `main`.

``` r
# Install the development version from r-universe
install.packages("gdalraster", repos = c("https://firelab.r-universe.dev", "https://cran.r-project.org"))
```

### From source code

#### Linux

GDAL \>= 3.1.0 built with GEOS is required, but a more recent version is
recommended.

On Ubuntu, recent versions of geospatial libraries can be installed from
the [ubuntugis-unstable
PPA](https://launchpad.net/~ubuntugis/+archive/ubuntu/ubuntugis-unstable)
with the following commands. Note that libxml2 is required for the R
package **xml2** which is a dependency, so we go ahead and install it
here as well:

    sudo add-apt-repository ppa:ubuntugis/ubuntugis-unstable
    sudo apt update
    sudo apt install libgdal-dev libgeos-dev libxml2-dev

The versions in ubuntugis-unstable generally work well and are more
up-to-date, but less recent versions in the [ubuntugis-stable
PPA](https://launchpad.net/~ubuntugis/+archive/ubuntu/ppa) could be used
instead.

Package **sf** provides helpful
[instructions](https://github.com/r-spatial/sf#linux) for installing the
geospatial libraries on other Linux distributions.

With the dependent libraries available on the system, install from CRAN:

``` r
install.packages("gdalraster")
```

Or install the development version from GitHub using package
[remotes](https://remotes.r-lib.org/):

``` r
remotes::install_github("firelab/gdalraster")
```

#### Windows

[RTools](https://cran.r-project.org/bin/windows/Rtools/) is needed to
install from source on Windows. RTools since version 4.2 includes GDAL
and all other dependent libraries that are needed to compile
**gdalraster**. Note that CRAN release periodic revisions to RTools that
often include updates to the libraries as new versions become available.
[Release
6691](https://cran.r-project.org/bin/windows/Rtools/rtools45/rtools.html)
of RTools 4.5 contains GDAL 3.11.4, GEOS 3.13.1 and PROJ 9.7.0.

With RTools installed:

``` r
# Install the development version from GitHub
remotes::install_github("firelab/gdalraster")
```

#### macOS

GDAL can be installed with Homebrew:

    brew install gdal

then

``` r
# Install the development version from GitHub
remotes::install_github("firelab/gdalraster")
```

It is not recommended to mix source installations and installation of
macOS binaries from CRAN. Consider installing the development version
from R-universe instead.

### Docker

The `r-gdalraster` build at
<https://github.com/mdsumner/gdal-builds/pkgs/container/gdal-builds> is
based on the GDAL [`ubuntu-full-latest`
image](https://github.com/OSGeo/gdal/tree/master/docker#full-ghcrioosgeogdalubuntu-full-latest-aliased-to-osgeogdal),
and adds the current released version of R along with development
version of **gdalraster** and its dependencies (thanks to Michael
Sumner):

    docker pull ghcr.io/mdsumner/gdal-builds:r-gdalraster

## Documentation

- [Reference Manual](https://firelab.github.io/gdalraster/reference/)
- [Raster API
  Tutorial](https://firelab.github.io/gdalraster/articles/raster-api-tutorial.html)
- [Vector API
  Overview](https://firelab.github.io/gdalraster/articles/vector-api-overview.html)
- [Using `gdal` CLI algorithms from
  R](https://firelab.github.io/gdalraster/articles/use-gdal-cli-from-r.html)
- [Raster Attribute
  Tables](https://firelab.github.io/gdalraster/articles/raster-attribute-tables.html)
- [Raster
  Display](https://firelab.github.io/gdalraster/articles/raster-display.html)
- [GDAL Block
  Caching](https://firelab.github.io/gdalraster/articles/gdal-block-cache.html)
- [GDAL Config Quick
  Ref](https://firelab.github.io/gdalraster/articles/gdal-config-quick-ref.html)
- [Vector Read
  Benchmarks](https://firelab.github.io/gdalraster/articles/vector-read-benchmarks.html)
