get.distances.prepaired: Find distances between points, for pairs of points already...

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 points, for pairs of points already organized as pairs.

Description

get.distances.prepaired returns all the distances between each specified pair of points.

Usage

get.distances.prepaired(pts)

Arguments

pts	A matrix or data.frame that has columns names 'fromlon', 'fromlat', 'tolon', 'tolat' with datum=WGS84 assumed.

Details

May need to fix cases where only a single row is input. This function returns a matrix or vector of distances, between points specified as pairs of lat/lon values. Points are specified using latitude and longitude in decimal degrees. Relies on the sp package for the spDistsN1 and SpatialPoints functions.

Value

Returns a vector of distances as numbers, in kilometers. Each element corresponds to one row in pts.

See Also

get.distances.all for a useful general function, get.distances for get.distances() which allows you to specify a search radius and get distances only within that radius which can be faster, 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

test.from <- structure(list(fromlat = c(38.9567309094, 38.9507043428, 38.0), 
 fromlon = c(-77.0896572305, -77.0896199948, -77.0)), 
 .Names = c("lat", "lon"), row.names = c("one", "two", "three"), 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("a", "b", "c"))
get.distances.prepaired(data.frame(
  fromlat=test.from$lat, fromlon=test.from$lon, tolat=test.to$lat, tolon=test.to$lon)
)

ejanalysis/proxistat documentation built on April 2, 2024, 10:13 a.m.