Calculate the angular difference between lines and a predefined bearing
This function was designed to find lines that are close to parallel and perpendicular to some pre-defined route. It can return results that are absolute (contain information on the direction of turn, i.e. + or - values for clockwise/anticlockwise), bidirectional (which mean values greater than +/- 90 are impossible).
angle_diff(l, angle, bidirectional = FALSE, absolute = TRUE)
l |
A spatial lines object |
angle |
an angle in degrees relative to North, with 90 being East and -90 being West. (direction of rotation is ignored). |
bidirectional |
Should the result be returned in a bidirectional format? Default is FALSE. If TRUE, the same line in the oposite direction would have the same bearing |
absolute |
If TRUE (the default) only positive values can be returned |
Building on the convention used in bearing() and in many applications,
North is definied as 0, East as 90 and West as -90.
Other lines:
geo_toptail(),
is_linepoint(),
line2df(),
line2points(),
line_bearing(),
line_breakup(),
line_match(),
line_midpoint(),
line_sample(),
line_segment(),
line_via(),
mats2line(),
n_sample_length(),
n_vertices(),
onewaygeo(),
points2line(),
toptail_buff(),
toptailgs(),
update_line_geometry()
lib_versions <- sf::sf_extSoftVersion()
lib_versions
# fails on some systems (with early versions of PROJ)
if (lib_versions[3] >= "6.3.1") {
# Find all routes going North-South
lines_sf <- od2line(od_data_sample, zones = zones_sf)
angle_diff(lines_sf[2, ], angle = 0)
angle_diff(lines_sf[2:3, ], angle = 0)
a <- angle_diff(flowlines, angle = 0, bidirectional = TRUE, absolute = TRUE)
plot(flowlines)
plot(flowlines[a < 15, ], add = TRUE, lwd = 3, col = "red")
# East-West
plot(flowlines[a > 75, ], add = TRUE, lwd = 3, col = "green")
}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.