sppt: Performs Andresen's Spatial Point Pattern Test

In wsteenbeek/sppt: Spatial Point Pattern Test

Description

This is a point pattern test that measures the degree of similarity at the local level between two spatial point patterns and is an area-based test.

Usage

sppt(
  base_points.sp,
  test_points.sp,
  uoa.sp,
  outputlist = FALSE,
  nsamples = 200,
  percpoints = 85,
  conf_level = 95,
  bootstrap = FALSE
)

Arguments

base_points.sp	the Base data of type SpatialPoints*
test_points.sp	the Test data of type SpatialPoints*
uoa.sp	the units of analysis of type SpatialPolygons*
outputlist	should the output of the function be a list, including all simulation runs as a matrix? default = FALSE
nsamples	number of samples in simulations, default = 200
percpoints	percentage of points used in simulations, default = 85
conf_level	confidence interval, default = 95
bootstrap	logical, default is FALSE

Details

In its default settings, the function is the original Andresen's sppt, so only Test data is randomly resampled (without replacement, by default using 85

By changing 'bootstrap' to TRUE, the 'percpoints' argument is ignored and the Test points are a bootstrapped sample: within each simualed dataset, as many points as the test set itself are sampled, but with replacement within each sample.

Value

When outputlist is FALSE (the default), returns the uoa.sp spatialobject including SPPT outcomes. When outputlist is TRUE (the default), returns a list with the first list element the uoa.sp spatialobject including SPPT outcomes, and the second list element a matrix of all nsamples simulations.

Examples

# Plot areas, base points data, and test points data
plot(areas.sp)
text(coordinates(areas.sp), label = areas.sp$ID)
text(coordinates(points1.sp), label = points1.sp$ID, col="blue")
text(coordinates(points2.sp), label = points2.sp$ID, col="red")

set.seed(76772)
myoutput <- sppt(base_points.sp = points1.sp, test_points.sp = points2.sp, uoa.sp = areas.sp)
summary_sppt(myoutput)
myoutput@data

# is exactly the same as:
set.seed(76772)
myoutput <- sppt(points1.sp, points2.sp, areas.sp,
                 outputlist=FALSE, nsamples=200, percpoints=85, conf_level=95)
myoutput@data

# now with a list being outputted, the 2nd element has all simulation outcomes
set.seed(76772)
myoutput <- sppt(points1.sp, points2.sp, areas.sp, outputlist = TRUE)
head(myoutput[[1]]@data) # same as previous
head(myoutput[[2]])

# Vancouver data
set.seed(9866)
myoutput <- sppt(vancouver_points1.sp, vancouver_points2.sp, vancouver_areas.sp)
summary_sppt(myoutput)

# Vancouver data, using a bootstrap approach instead of Andresen's subsampling method
set.seed(9866)
myoutput <- sppt(vancouver_points1.sp, vancouver_points2.sp, vancouver_areas.sp, bootstrap = TRUE)
summary_sppt(myoutput)

wsteenbeek/sppt documentation built on Oct. 16, 2020, 6:11 p.m.