Get the support of a pgeometry object

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

Usage

spa_support(pgo)

Arguments

pgo

A pgeometry object of any type.

Value

An sfg object that represents the support of pgeometry. It can be an empty object, if pgeometry is empty.

Details

The spa_support() function employs the classical definition of support from the fuzzy set theory in the context of Spatial Plateau Algebra. The support only comprises the points with membership degree greater than or equal to 1. Hence, spa_support() returns the sfg object that represents the total extent of the pgeometry given as input. If the pgeometry is empty, 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 support
spa_support(ppoint)
#> MULTIPOINT ((0 0), (0 0.5), (1 1), (1 2), (1 3), (2 0), (2 1), (2 2), (2 3), (2 4), (3 1), (3 2), (3 3))

# Getting the support of an empty pgeometry
spa_support(create_empty_pgeometry("PLATEAUREGION"))
#> MULTIPOLYGON EMPTY