angleRemap {oce} | R Documentation |
Convert an angle from the 0:360 range to -180:180
angleRemap(theta)
theta |
an angle (in degrees) that is in the range from 0 to 360 degrees |
This is mostly used for instrument heading angles, in cases where the instrument is aligned nearly northward, so that small variations in heading (e.g. due to mooring motion) can yield values that swing from small angles to large angles, because of the modulo-360 cut point.
The method is to use the cosine and sine of the angle in order to
find "x" and "y" values on a unit circle, and then to use
atan2
to infer the angles.
A vector of angles, in the range -180 to 180.
Dan Kelley
library(oce) ## fake some heading data that lie near due-north (0 degrees) n <- 20 heading <- 360 + rnorm(n, sd=10) heading <- ifelse(heading > 360, heading - 360, heading) x <- 1:n plot(x, heading, ylim=c(-10, 360), type='l', col='lightgray', lwd=10) lines(x, angleRemap(heading))