Calculates the angle (in radians) of the rotation taking one orientation to
another.
Usage
rotation.angle(x)
rotation.distance(x, y)
Arguments
x,y
Two orientation objects
Value
rotation.distance returns a vector of length max(length(x), length(y))
containing the
angle of the rotation taking corresponding elements of x to y (with the
usual recycling rules if they are different lengths).
rotation.angle is equivalent to calculating the rotation.distance to the
identity matrix.
Details
If y is missing in a call to rotation.distance,
it is treated as the identity, i.e.
rotation.angle(x) is calculated.