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A mlr3::DataBackend for vector objects (only package sf is supported).

Super class

mlr3::DataBackend -> DataBackendVector

Public fields

compact_seq

logical(1)
If TRUE, row ids are a natural sequence from 1 to nrow(data) (determined internally). In this case, row lookup uses faster positional indices instead of equi joins.

Active bindings

rownames

(integer())
Returns vector of all distinct row identifiers, i.e. the contents of the primary key column.

colnames

(character())
Returns vector of all column names, including the primary key column.

nrow

(integer(1))
Number of rows (observations).

ncol

(integer(1))
Number of columns (variables), including the primary key column.

geometry

(integer(1))
Returns the sf geometry.

Methods

Inherited methods


Method new()

Creates a backend for spatial vector objects.

Usage

DataBackendVector$new(data, primary_key = NULL)

Arguments

data

(sf)
A raster object.

primary_key

(character(1) | integer())
Name of the primary key column, or integer vector of row ids.


Method data()

Returns a slice of the data in the specified format. Currently, the only supported formats are "data.table" and "Matrix". The rows must be addressed as vector of primary key values, columns must be referred to via column names. Queries for rows with no matching row id and queries for columns with no matching column name are silently ignored. Rows are guaranteed to be returned in the same order as rows, columns may be returned in an arbitrary order. Duplicated row ids result in duplicated rows, duplicated column names lead to an exception.

Usage

DataBackendVector$data(rows, cols, data_format = "data.table")

Arguments

rows

integer()
Row indices.

cols

character()
Column names.

data_format

(character(1))
Desired data format, e.g. "data.table" or "Matrix".


Method head()

Retrieve the first n rows.

Usage

DataBackendVector$head(n = 6L)

Arguments

n

(integer(1))
Number of rows.

Returns

data.table::data.table() of the first n rows.


Method distinct()

Returns a named list of vectors of distinct values for each column specified. If na_rm is TRUE, missing values are removed from the returned vectors of distinct values. Non-existing rows and columns are silently ignored.

Usage

DataBackendVector$distinct(rows, cols, na_rm = TRUE)

Arguments

rows

integer()
Row indices.

cols

character()
Column names.

na_rm

logical(1)
Whether to remove NAs or not.

Returns

Named list() of distinct values.


Method missings()

Returns the number of missing values per column in the specified slice of data. Non-existing rows and columns are silently ignored.

Usage

DataBackendVector$missings(rows, cols)

Arguments

rows

integer()
Row indices.

cols

character()
Column names.

Returns

Total of missing values per column (named numeric()).