coords: Geographic Coordinate Class

Description

as_coords() creates an object of class "coords", a robust representation of a series of geographic or GPS coordinate values.

latlon()<- adds information to objects of class "coords" specifying whether individual coordinate values represent latitude or longitude.

Usage

as_coords(object, ...)
# S3 method for default
as_coords(object, ..., fmt = 1L)
latlon(cd) <- value
# S3 method for waypoints
as_coords(object, which, ...)

Value

as_cords() returns an object of class "coords", comprising a numeric vector argument with additional attributes: –

"class": the character string "coords".
"fmt": an integer representing the coordinate format.
"valid": a logical vector indicating whether individual coordinate values are valid geographic locations.

The as_cords() method for class "coords" returns its numeric vector argument object modified in place, whereas the method for class 'waypoints' returns a new numeric vector.

latlon() returns its "coords" argument cd with a logical vector attribute "latlon" added or updated to reflect argument value.

Arguments

object: a numeric vector of coordinate values, optionally named, or an object of class "waypoints".
...: further arguments passed to or from other methods.
fmt: integer, 1L, 2L or 3L, specifying the required coordinate format.
cd: object of class "coords" created by function as_coords().
value: a logical vector of length 1 or length(x).
which: logical, indicating whether the as_coords() method for class "waypoints" extracts the latitude component of argument object (if TRUE), or the longitude (if FALSE).

Details

Individual values provided in a numeric vector argument object should have a decimal point after the number of whole degrees in the case of decimal degrees, after the number of whole minutes in the case of degrees and minutes, and after the number of whole seconds in the case of degrees, minutes and seconds.

The fmt argument should be 1L to represent decimal degrees, 2L for degrees and minutes, and 3L for degrees, minutes and seconds and is used to provide the format of values in the numeric vector argument object to be converted to class "coords".

The values of a newly created "coords" object are checked to ensure they are valid geographic locations as described under validate().

Individual coordinate values in a Coords object may be specified as representing latitude or longitude using latlon(). The value argument may either be a single value, TRUE signifying that all values are latitude, FALSE signifying that all values are longitude, or a logical vector of the same length as as the Coords object signifying whether individual values are latitude or longitude.

Examples

Run this code

## Numeric vector representing degrees and minutes, with
## the decimal point after the number of whole minutes
dm <- c(5130.4659, 4932.7726, 4806.4339, 3853.3696, 0.0000, -3706.7044, -5306.2869, -2514.4093,
        -007.6754, 1823.9137, -12246.7203, -7702.1145, 0.0000, -1217.3178, 7331.0370, -5731.1536)

## Create an unnamed "coords" object in degrees and minutes (fmt = 2)
## (Latitude and longitude unspecified)
as_coords(dm, fmt = 2)

## Name the "coords" object
names(dm) <- rep(c("Nelson's Column", "Ostravice", "Tally Ho", "Washington Monument", "Null Island",
                   "Tristan da Cunha", "Mawson Peak", "Silvio Pettirossi International Airport"), 2)
dm

## Set all values to represent longitude
## ("latlon" attribute set to FALSE, length 1)
latlon(dm) <- FALSE
dm

## Set eight values each of latitude and longitude
## ("latlon" attribute set to TRUE, n=8, and FALSE, n=8)
latlon(dm) <- rep(c(TRUE, FALSE), each = 8)
dm

## Show as an ordinary R numeric vector
as.numeric(dm)

rm(dm)