m.surround: A function to generate m-surroundings

In rominsal/spqdata: Testing for spatial structure of qualitative data in cross section

Description

This function obtains the m-surroundings by selecting the m-1 nearest neighbors of each observation, allowing for a degree of overlap of r.

Usage

m.surround(x, m, r = 1, distance = "Euclidean", control = list())

Arguments

x	input sf object with points/multipolygons geometry or matrix of spatial coordinates
m	dimension of m-surrounding
r	maximum overlapping between any two m-surroundings.
distance	character. For Cartesian coordinates only: one of Euclidean, Hausdorff or Frechet; for geodetic coordinates, Great Circle distances are computed.
control	optional. Parameters for pruning m-surroundings with the aim of remove m-surroundings whose elements are too far.

Details

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Value

A list of class list and m_surr containing the following components:

ms	a matrix. Each row is a m-surrounding.
R	total number of observations.
mdtms	xxxxxxxxxxxxxxxxxxx.
mscbl	xxxxxxxxxxxxxxxxxxx.
rowexcl	xxxxxxxxxxxxxxxxxxx.
N	total number of symbolized observations.
m	length of the m-surroundings.
r	overlapping degree.
initobs	element to star the generation of m-surroundings. default initobs=1.
distance	distance select to prune the m-surroundings.
m	length of the m-surroundings.
x	the input "x" as sf-object.

Control arguments

distance

character to select the type of distance. Default = "Euclidean" for Cartesian coordinates only: one of Euclidean, Hausdorff or Frechet; for geodetic coordinates, great circle distances are computed (see sf::st_distance())

dtmaxabs

xxxxxxxxxxxxxxxxxxxxxxxxxxxx

dtmaxpc

xxxxxxxxxxxxxxxxxxxxxxxxxxxx

dtmaxknn

Elimina m-surrounding donde alguno de los elementos no está entre los knn más próximos

Author(s)

Fernando López	[e-mail]
Román Mínguez	[e-mail]
Antonio Páez	[e-mail]
Manuel Ruiz	[e-mail]

References

• Ruiz M, López FA, A Páez. (2010). Testing for spatial association of qualitative data using symbolic dynamics. Journal of Geographical Systems. 12 (3) 281-309

Examples

Example 1: Obtain m-surroundings with degree of overlapping r
rm(list = ls())
N <- 100
cx <- runif(N)
cy <- runif(N)
x <- cbind(cx,cy)
m = 3
r = 1
msurr_points <- m.surround(x = x, m = m, r = r)
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)
summary(msurr_points)
msurr_points <- m.surround(x = x, m = m, r = r,control = list(dtmaxpc = 0.1))
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)
summary(msurr_points)
msurr_points <- m.surround(x = x, m = m, r = r,control = list(dtmaxknn = 20))
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)
summary(msurr_points)

Example 2:
rm(list = ls())
data("FastFood")
m = 3
r = 1
msurr_points <- m.surround(x = FastFood.sf, m = m, r = r, distance = "Euclidean", control = list(dtmaxpc = .1))
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)
print(msurr_points)
summary(msurr_points)
msurr_points <- m.surround(x = FastFood.sf, m = m, r = r, distance = "Euclidean", control = list(dtmaxknn = 20))
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)
summary(msurr_points)

Example 3: With isolated areas
rm(list = ls())
data(Spain)
plot(sf::st_geometry(spain.sf))
m = 3
r = 1
msurr_points <- m.surround(x = spain.sf, m = m, r = r, distance = "Euclidean", control = list(dtmaxknn = 8))
plot(msurr_points, type = 1)
plot(msurr_points, type = 2)

Example 4: Examples with multipolygons
rm(list = ls())
fname <- system.file("shape/nc.shp", package="sf")
nc <- st_read(fname)
plot(sf::st_geometry(nc))
m = 3
r = 1
msurr_polygonsf <- m.surround(x = nc, m = m, r = r,distance = "Great Circle", control=list(dtmaxpc = 0.20))
plot(msurr_polygonsf, type = 1)
plot(msurr_polygonsf, type = 2)

Example 5: With regular lattice
rm(list = ls())
sfc = st_sfc(st_polygon(list(rbind(c(0,0), c(1,0), c(1,1), c(0,1), c(0,0)))))
hexs <- st_make_grid(sfc, cellsize = 0.1, square = FALSE)
hexs.sf <- st_sf(hexs)
listw  <- poly2nb(as(hexs.sf, "Spatial"), queen = FALSE)
m = 3
r = 1
msurr_polygonsf <- m.surround(x = hexs.sf, m = m, r = r)
plot(msurr_polygonsf, type = 1)
plot(msurr_polygonsf, type = 2)
summary(msurr_polygonsf)

rominsal/spqdata documentation built on Jan. 24, 2021, 11:11 a.m.