proxistat-package: Find Distances between lat lon Points or Create Proximity...

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)

Find Distances between lat lon Points or Create Proximity Scores.

Description

This package has functions helping to calculate distances between points, such as the distances between all points, distances to all points within some maximum distance, distance to nearest single point, etc. It also can create a proximity score for each spatial unit like a Census block group, to quantify the distance-weighted count of nearby points.

Details

This package has functions helping to calculate distances between geographic points, such as the distances between all points, distances to all points within some maximum distance, distance to nearest single point, etc. It also can create a proximity score for each spatial unit like a Census block group, to quantify the distance-weighted count of nearby points. This proximity score can be used in environmental justice (EJ) analysis, for example.

This package relies on the sp package for the actual calculation of distance.

A vector of points can be specified using a data.frame of two columns, "lat" and "lon" which specify latitude and longitude in decimal degrees. It returns the distances from one or more frompoints to one or more topoints.

Key functions include

• get.nearest to find the one among topoints nearest each frompoints

• get.distances to find distances quickly within an optional search radius

• proxistat to create a proximity score that quantifies, for each spatial unit like a Census block group, how many topoints are nearby and how close they are

• convert to convert units (miles, km)

Author(s)

[e-mail]<[e-mail]>

References

http://ejanalysis.github.io
http://www.ejanalysis.com/
sp package documentation for basic distance function.
Some discussion of this type of proximity indicator is available in the EJSCREEN mapping tool documentation:
U.S. Environmental Protection Agency (2015). EJSCREEN Technical Documentation. http://www.epa.gov/ejscreen
http://en.wikipedia.org/wiki/Longitude and http://en.wikipedia.org/wiki/Decimal_degrees

See Also

sp, US block points dataset: http://ejanalysis.github.io/UScensus2010blocks/, deltalon.per.km, deltalon.per.km, meters.per.degree.lat, meters.per.degree.lon

Examples

test.from <- structure(list(fromlat = c(38.9567309094, 38.9507043428),
  fromlon = c(-77.0896572305, -77.0896199948)),
  .Names = c("lat","lon"), row.names = c("6054762", "6054764"), class = "data.frame")
test.to <- structure(list(tolat = c(38.9575019287, 38.9507043428, 38.9514152435),
  tolon = c(-77.0892818598, -77.0896199948, -77.0972395245)),
  .Names = c("lat","lon"), class = "data.frame", row.names = c("6054762", "6054763", "6054764"))
  setseed(999)
t100=testpoints(100)
t10=testpoints(10)
t3=testpoints(3)

get.distances(
  test.from[1:2,], test.to[1:3, ], radius=0.7, units='km', return.rownums=TRUE, return.latlons=TRUE
)
get.nearest(test.from, test.to)

get.distances(  t3, t10, units='km', return.crosstab=TRUE)
get.distances(  t3, t10, units='km')
get.distances(  t3, t10, radius=300, units='km')
proxistat(t3, t10, radius = 300, units = "km", area = c(100001:100003)) 
proxistat(  t3, t10, radius=300, units='km')
1/get.nearest(   t3, t10, radius=300, units='km')

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