makePlanar: Project Geographic Coordinates onto a Plane

In contact: Creating Contact and Social Networks

Description

This function converts lon/lat data (decimal degrees) from a geographic coordinate system to planar coordinates using a custom azimuthal equidistant projection, and appends these new coordinates to an input data frame (x). By default, the function assumes longitude and latitude coordinates were produced using the WGS84 datum, but users may change this datum if they wish.

Usage

makePlanar(
  x = NULL,
  x.lon = NULL,
  x.lat = NULL,
  origin.lon = NULL,
  origin.lat = NULL,
  datum = "WGS84"
)

Arguments

x	Data frame or matrix containing geographic data. Defaults to NULL.
x.lon	Vector of length(nrow(x)) or singular character data, detailng the relevant colname in x, that denotes what longitude information will be used. If argument == NULL, makePlanar assumes a column with the colname "lon" exists in x. Defaults to NULL.
x.lat	Vector of length(nrow(x)) or singular character data, detailing the relevant colname in x, that denotes what latitude information will be used. If argument == NULL, makePlanar assumes a column with the colname "lat" exists in x. Defaults to NULL.
origin.lon	Numerical. Describes the longitude will be used as the origin-point longitude for the azimuthal-equidistant projection. If NULL, defaults to the longitude of the data set's centroid. Defaults to NULL.
origin.lat	Numerical. Describes the latitude will be used as the origin-point latitude for the azimuthal-equidistant projection. If NULL, defaults to the latitude of the data set's centroid. Defaults to NULL.
datum	Character string describing the datum used to generate x.lon and x.lat. Defaults to "WGS84."

Details

Users may specify longitude and latitude coordinates to become the origin of the projection (i.e., the (0,0) coordinate). If they do not specify these values, however, the function calculates the centroid of the data and will use this as the origin point.

Note: this function does not allow any NA coordinate values in longitude/latitude vectors. If NAs exist you will get the following error: "Error in .local(obj, ...) : NA values in coordinates." If NAs exist in your data, we suggest 1.) removing them, or 2.) smoothing data using contact::tempAggregate prior to running this function.

Value

Output is x appended with the following columns:

planar.x	Planar x-coordinate values derived from longitude observations.
planar.y	Planar y-coordinate values derived from latitude observations.
origin.lon	Longitude of the origin point, either user specified or the longitude of the data's centroid.
origin.lat	Latitude of the origin point, either user specified or the latitude of the data's centroid.
origin.distance	Linear distance (m) between every point and the origin point.

Examples

data(baboons)

head(baboons) #see that locations are in geographic coordinates

lon.na <- which(is.na(baboons$location.long) == TRUE) #pull row ids of lon NAs
lat.na <- which(is.na(baboons$location.lat) == TRUE) #pull row ids of lat NAs

baboons.naRM <- droplevels(baboons[-unique(c(lon.na, lat.na)),]) #remove NAs

baboons.naRM_planar <- makePlanar(x = baboons.naRM, 
   x.lon = baboons.naRM$location.long, x.lat = baboons.naRM$location.lat, 
   origin.lon = NULL, origin.lat = NULL, datum = "WGS84") #note no specified origin coords
   
head(baboons.naRM_planar) #see that planar coordinates are reported

contact documentation built on May 17, 2021, 5:07 p.m.