testpoints: Generate a number of randomly placed points, as...

In ejanalysis/proxistat: Create a Proximity Score in Each Census Unit, Based on Distances to Specified Points (as in EPA's EJScreen tool, for example)

Generate a number of randomly placed points, as latitude/longitude values.

Description

Generate a number of randomly placed points, as latitude/longitude values.

Usage

testpoints(
  n = 1,
  weighting = "area",
  ST,
  as.df = TRUE,
  minlat = 17.9,
  maxlat = 71.25,
  minlon = -175.89,
  maxlon = 178.34,
  useblocks = FALSE
)

Arguments

n	Numeric value, 1 by default. Specifies how many testpoints to return. Must be an integer between zero and 50 million, and not NA.
weighting	area or people or geo or degrees text indicating what type of weighting, by area or people or geo (each block or block group has equal chance). Default is area - a random square mile not a random residence or random Census geometry.
ST	optional vector of 2 letter state abbreviations, to limit it to some state(s). Default is all USA (including PR I think).
as.df	Logical, default is TRUE, in which case returns a data.frame, otherwise a matrix.
minlat	the minimum latitude in decimal degrees to use for generating random points within some range.
maxlat	the maximum latitude in decimal degrees to use for generating random points within some range.
minlon	the minimum longitude in decimal degrees to use for generating random points within some range.
maxlon	the maximum longitude in decimal degrees to use for generating random points within some range.
useblocks	logical, whether to use the several million Census blocks if TRUE (2020 Census as of 11/2022) or just the approx 220k block groups (from github package ejscreen) if FALSE which is faster

Details

This function returns n points at random location latitude and longitude values, weighted by area or by population count in block group, to be roughly representative of either a random location (like throwing a dart, equal weight per square mile of land area - does not include water area in weighting but can return a point in water if bg has internal point in water?!) or where a randomly selected US resident lives (population weighted). Points are returned as latitude and longitude in decimal degrees.

For people weighted, it picks from the Census blockgroup internal points, which are much more representative of where people live than a random square mile would be.

Value

By default, returns a data.frame (or matrix if as.df=FALSE) that has 2 columns: lat and lon, in decimal degrees, with 1 row per point.

See Also

get.distances.all which allows you to get distances between all points, get.distances.prepaired for finding distances when data are already formatted as pairs of points, get.nearest which finds the distance to the single nearest point within a specified search radius instead of all topoints, and proxistat which calculates a proximity score for each spatial unit based on distances to nearby points.

Examples

testpoints(19,minlat=47,maxlat=48)
get.distances(testpoints(100),testpoints[10],radius=999,return.rownums=TRUE,return.latlons=TRUE)

ejanalysis/proxistat documentation built on Jan. 1, 2025, 10:02 a.m.