Get the core of a pgeometry object

spa_core() yields a crisp spatial object (as an sfg object) that corresponds to the core of a pgeometry object given as input.

Usage

spa_core(pgo)

Arguments

pgo

A pgeometry object of any type.

Value

An sfg object that represents the core of pgo. It can be an empty object, if pgo does not have a component with membership degree 1.

Details

The spa_core() function employs the classical definition of core from the fuzzy set theory in the context of Spatial Plateau Algebra. The core only comprises the points with membership degree equal to 1. Hence, this operation returns the sfg object that represents the component labeled with membership degree equal to 1 of the pgeometry object given as input. If the pgeometry object has no core, then an empty sfg object is returned.

References

Carniel, A. C.; Venâncio, P. V. A. B; Schneider, M. fsr: An R package for fuzzy spatial data handling. Transactions in GIS, vol. 27, no. 3, pp. 900-927, 2023.

Underlying concepts and formal definitions of Spatial Plateau Algebra are introduced in:

• Carniel, A. C.; Schneider, M. Spatial Plateau Algebra: An Executable Type System for Fuzzy Spatial Data Types. In Proceedings of the 2018 IEEE International Conference on Fuzzy Systems (FUZZ-IEEE 2018), pp. 1-8, 2018.

Examples

pcp1 <- create_component("POINT(0 0)", 0.3)
pcp2 <- create_component("MULTIPOINT((2 2), (2 4), (2 0))", 0.5)
pcp3 <- create_component("MULTIPOINT((1 1), (3 1), (1 3), (3 3))", 0.9)
pcp4 <- create_component("MULTIPOINT((1 2), (2 1), (3 2))", 1)
pcp5 <- create_component("MULTIPOINT((0 0.5), (2 3))", 0.7)
pcp6 <- create_component("MULTIPOINT((0 1), (3 3.5))", 0.85)
pcp7 <- create_component("MULTIPOINT((1 0), (4 2))", 0.4)

# Creating a plateau point object
ppoint <- create_pgeometry(list(pcp1, pcp2, pcp3, pcp4, pcp5), "PLATEAUPOINT")
ppoint
#> [1] "PLATEAUPOINT ((POINT (0 0), 0.3), (MULTIPOINT ((2 2), (2 4), (2 0)), 0.5), (MULTIPOINT ((0 0.5), (2 3)), 0.7), (MULTIPOINT ((1 1), (3 1), (1 3), (3 3)), 0.9), (MULTIPOINT ((1 2), (2 1), (3 2)), 1))"

# Getting its core
spa_core(ppoint)
#> MULTIPOINT ((1 2), (2 1), (3 2))

# Getting the core of an empty pgeometry
spa_core(create_empty_pgeometry("PLATEAUREGION"))
#> POLYGON EMPTY