Circular distribution
In probability and statistics, a circular distribution or polar distribution is a probability distribution of a random variable whose values are angles, usually taken to be in the range [0, 2π). A circular distribution is often a continuous probability distribution, and hence has a probability density, but such distributions can also be discrete, in which case they are called circular lattice distributions. Circular distributions can be used even when the variables concerned are not explicitly angles: the main consideration is that there is not usually any real distinction between events occurring at the lower or upper end of the range, and the division of the range could notionally be made at any point.
Graphical representation
If a circular distribution has a density
it can be graphically represented as a closed curve
where the radius 
is set equal to
and where a and b are chosen on the basis of appearance.
Example
By computing the probability distribution of angles along a handwritten ink trace,
a lobe-shaped polar distribution emerges. The main direction of the lobe in the
first quadrant corresponds to the slant of handwriting (see: graphonomics).
