fsr (version 1.0.0)

spa_eval: Capturing the membership degree of a point

Description

This function evaluates the membership degree of a given point in a spatial plateau object of any type. It returns a value in [0, 1] that indicates to which extent the point belongs to the pgeometry object.

Usage

spa_eval(pgo, point)

Arguments

pgo

A pgeometry object of any type.

point

An sfg object of the type POINT.

Value

A numeric value between 0 and 1 that indicates the membership degree of a point (i.e., sfg object) in a spatial plateau object (i.e., pgeometry object).

Details

The goal of this function is to return the membership degree of a simple point object (i.e., sfg object) in a given spatial plateau object (i.e., pgeometry object). This evaluation depends on the following basic cases:

• if the simple point object belongs to the interior or boundary of one component of the spatial plateau object, it returns the membership degree of that component.

• if the simple point object intersects more components (e.g., boundaries of region components, or different line components), it returns the maximum membership degree of all intersected components.

• if the simple point object is disjoint to the support of the spatial plateau object, it returns 0.

References

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

# NOT RUN {
library(tibble)
library(sf)
library(FuzzyR)

# some basic examples 

pts1 <- rbind(c(1, 2), c(3, 2))
pts2 <- rbind(c(1, 1), c(2, 3), c(2, 1))
pts3 <- rbind(c(2, 2), c(3, 3))

cp1 <- component_from_sfg(st_multipoint(pts1), 0.3)
cp2 <- component_from_sfg(st_multipoint(pts2), 0.6)
cp3 <- component_from_sfg(st_multipoint(pts3), 1.0)

pp <- create_pgeometry(list(cp1, cp2, cp3), "PLATEAUPOINT")

spa_eval(pp, st_point(c(1, 2)))
spa_eval(pp, st_point(c(1, 3)))

# other examples with plateau regions

set.seed(345)

# some random points to create plateau region objects by using the function spa_creator
tbl = tibble(x = runif(10, min= 0, max = 20), 
             y = runif(10, min = 0, max = 30), 
             z = runif(10, min = 0, max = 100))

#getting the convex hull on the points to clipping the construction of plateau region objects
pts <- st_as_sf(tbl, coords = c(1, 2))
ch <- st_convex_hull(do.call(c, st_geometry(pts)))

pregions <- spa_creator(tbl, fuzz_policy = "fcp", k = 2, base_poly = ch)

# capturing the membership degree of a specific point in each object
spa_eval(pregions$pgeometry[[1]], st_point(c(5, 15)))
spa_eval(pregions$pgeometry[[2]], st_point(c(5, 15)))

# }