artif_spo {stppSim}

Artificial spatial origins

Description

Simulates spatial locations to serve as origins of walkers. If provided, spaces covered by restriction features are avoided. Final origins are assigned probability values indicating the strengths of the origins.

Usage

artif_spo(poly, n_origin=50, restriction_feat = NULL,
n_foci=5, foci_separation = 10, mfocal = NULL,
conc_type = "nucleated", p_ratio)

Arguments

poly

(An sf or S4 object) a polygon shapefile defining the extent of the landscape

n_origin

number of locations to serve as origins for walkers. Default:50.

restriction_feat

(An S4 object) optional shapefile containing features in which walkers cannot walk through. Default: NULL.

n_foci

number of focal points amongst the origin locations. The origins to serve as focal points are based on random selection. n_foci must be smaller than n_origins.

foci_separation

a value from 1 to 100 indicating the nearness of focal points to one another. A 0 separation indicates that focal points are in close proximity of one another, while a 100 indicates focal points being evenly distributed across space.

mfocal

the c(x, y) coordinates of a single point, representing a pre-defined main focal point (origin) in the area. The default is NULL in which a random coordinate is chosen within the polygon area.

conc_type

concentration of the rest of the origins (non-focal origins) around the focal ones. The options are "nucleated" and "dispersed".

p_ratio

the smaller of the two terms of proportional ratios. For example, a value of 20 implies 20:80 proportional ratios.

Details

The focal origins (n_foci) serve as the central locations (such as, city centres). The foci_separation indicates the nearness of focal origins from one another. The conc_type argument allows a user to specify the type of spatial concentration exhibited by the non-focal origin around the focal ones. If restriction_feat is provided, its features help to prevent the occurrence of any events in the areas occupied by the features.

Value

Returns a list detailing the properties of the generated spatial origins with associated strength (probability) values.

Examples

#load boundary of Camden
load(file = system.file("extdata", "camden.rda",
package="stppSim"))
boundary = camden$boundary # get boundary
landuse <- camden$landuse
spo <- artif_spo(poly = boundary, n_origin = 50,
restriction_feat = landuse, n_foci=5, foci_separation = 0,
mfocal = NULL, conc_type = "dispersed", p_ratio=20)