Skip to contents

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

Source: R/simutil-vector_heading.r
vector_heading.Rd

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).

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.

Details

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

Note

This function is called from within crw_in_polygon()

Author

C. Holbrook (cholbrook@glfc.org)

Examples


# example using generic cartesian (regular grid) coordinates
x <- c(2, 4)
y <- c(2, 4)
vector_heading(x, y)
#> [1] 45

x2 <- c(2, 4, 2)
y2 <- c(2, 4, 2)
vector_heading(x2, y2)
#> [1]  45 225


# 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"
)
#> [1] 104.6800 244.9958

# example using the x-only input method
vector_heading(
  x = path1[, c("longitude", "latitude")],
  coord_sys = "longlat"
)
#> [1] 104.6800 244.9958