Interface to the QGIS Project

The QgisProject class provides an R6 interface to interact with the currently active QGIS project. It allows reading project properties, listing layers, and transferring spatial data between R and QGIS.

Details

Please note that you should not instantiate this class manually using QgisProject$new(). Instead, use the public wrapper function qgis_project() to safely establish the connection.

Active bindings

title

(character) The title of the QGIS project (read-only).

path

(character) The absolute path to the QGIS project file (read-only).

crs

(character) The authority ID of the project's CRS (e.g., "EPSG:4326") (read-only).

units

(character) The map units of the project (e.g., "meters") (read-only).

Methods

Public methods

• QgisProject$new()

• QgisProject$list_layers()

• QgisProject$get_layer()

• QgisProject$insert_layer()

• QgisProject$layer_info()

• QgisProject$get_canvas_extent()

• QgisProject$get_selected_features()

• QgisProject$print()

• QgisProject$clone()

---

Method new()

Create a new QgisProject object. This is typically instantiated via qgis_project().

Usage

QgisProject$new(data = NULL)

Arguments

data

A list containing the initial project state. If NULL, it will be requested from QGIS. For internal use.

Returns

A new QgisProject object.

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Method list_layers()

Lists layers available in the current QGIS project.

Usage

QgisProject$list_layers(type = NULL)

Arguments

type

(integer) An optional filter for layer type. Corresponds to QgsMapLayerType: 0 for vector, 1 for raster. Use NULL to list all layers.

Returns

A data frame with the name and id of the layers.

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Method get_layer()

Reads a QGIS layer and loads it into R as a spatial object.

Usage

QgisProject$get_layer(x, ...)

Arguments

x

(character) The name or ID of the layer to get.

...

Additional arguments passed to sf::st_read() for vector layers.

Returns

An sf object for vector layers or a SpatRaster object from the terra package for raster layers.

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Method insert_layer()

Inserts an R spatial object into the QGIS project as a new layer.

Usage

QgisProject$insert_layer(layer, name = NULL, ...)

Arguments

layer

The spatial object to insert. Must be an sf object or a SpatRaster from the terra package.

name

(character) The desired name for the new layer in QGIS. If NULL, a name will be generated from the object's variable name.

...

Additional arguments passed to sf::st_write() for vector layers.

Returns

The QgisProject object, invisibly.

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Method layer_info()

Prints detailed information about a specific layer.

Usage

QgisProject$layer_info(x)

Arguments

x

(character) The name or ID of the layer.

Returns

The QgisProject object, invisibly.

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Method get_canvas_extent()

Gets the extent of the current map canvas.

Usage

QgisProject$get_canvas_extent()

Returns

A bbox object from the sf package representing the current view extent.

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Method get_selected_features()

Gets the selected features from the currently active vector layer in QGIS.

Usage

QgisProject$get_selected_features()

Returns

An sf object containing the selected features. Returns an error if the active layer is not a vector layer or has no selection.

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Method print()

Prints a summary of the QGIS project information.

Usage

QgisProject$print(...)

Arguments

...

Ignored.

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Method clone()

The objects of this class are cloneable with this method.

Usage

QgisProject$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.