RegionSelection-class: The 'ItemSelection' class implements 'Selection' for the...

In plumbr: Mutable and Dynamic Data Models

The ItemSelection class implements Selection for the selection of 1D and 2D regions in plot/data space.

Description

The ItemSelection class implements Selection for the selection of 1D and 2D regions in plot/data space.

Constructor

• RegionSelection(delegate = NULL): Constructs an RegionSelection object with the underlying selection provided by delegate, which may be a function or any other R object. If it is not a function, delegate must support coercion to a matrix as described in the next section. However, delegate is usually a function that is invoked whenever the selection is stored or retrieved. If the function is called with no arguments, it should return the selection. Otherwise, the argument is the new selection status, and the function should store it. This is the same semantic as active bindings. This dynamic functionality allows proxying of other Selection objects or external sources, such as a selection model from a GUI toolkit.

Interpreting the Selection

Any R object can represent the underlying selection, so for simplicity we recommend that the client interpret the selection through coercion. Currently, there is only one supported coercion of RegionSelection:

• as.matrix(x): returns a matrix with a column for each dimension and a row for each point. In the 2D case, the points describe one or more polygons. As with the polygon function, polygons are separated by rows of NA, and the last point is connected with the first. In the 1D case, the single column might encode, for example, selections of factor levels in an area plot.

We will probably need to add more coercions as use cases arise. This is still very preliminary.

Supported Selection Calculus

For now, RegionSelection only supports the add operation described in the documentation for Selection.

Author(s)

Michael Lawrence

See Also

Selection for the rest of the details.

Examples

## forthcoming

plumbr documentation built on May 7, 2022, 1:05 a.m.