vector_heading: Calculate direction (heading) of a vector (in degrees)

In jsta/glatos: A package for the Great Lakes Acoustic Telemetry Observation System

Calculate direction (heading) of a vector (in degrees)

Description

Calculate direction (heading) of each link of a vector (in degrees)

Usage

vector_heading(x, y = NULL, coord_sys = NA)

Arguments

x	A numeric vector of x coordinates; minimum of 2. OR A two-column matrix or data frame with x coordinates in column 1 and y coordinates in column 2.
y	A numeric vector of y coordinates; minimum of 2.
coord_sys	The type of geographical coordinate system used. Possible values are 'NA' (for any cartesian grid; e.g., UTM) or 'longlat' (for WGS84 in decimal degrees).

Details

Calculates direction (in degrees) for each of k-1 vectors, where k = length(x) - 1. Lengths of x and y must be equal.

Value

A numeric scalar with heading in degrees or a numeric vector of headings if length(x) > 2.

If units are decimal degrees (i.e., coord_sys = "longlat") then the angles returned will represent the heading at the start of each vector.

Note

This function is called from within crw_in_polygon

Author(s)

C. Holbrook ([e-mail])

Examples

#example using generic cartesian (regular grid) coordinates
x=c(2,4)
y=c(2,4)
vector_heading(x, y)

x2=c(2,4,2)
y2=c(2,4,2)
vector_heading(x2, y2)


#example using WGS84 lat-lon
#e.g., from Duluth to Toronto to Detroit 

path1 <- data.frame(city = c("Duluth", "Toronoto", "Detroit"),
                    longitude = c(-92.1005, -79.3832, -83.0458),
                    latitude = c(46.7867, 43.6532, 42.3314))

#example using the x, y input method way
vector_heading(x = c(-92.1005, -79.3832, -83.0458), 
               y = c(46.7867, 43.6532, 42.3314), 
               coord_sys = "longlat")
               
#example using the x-only input method
vector_heading(x = path1[ , c("longitude", "latitude")], 
               coord_sys = "longlat")

jsta/glatos documentation built on July 11, 2022, 7:01 a.m.