Draw random angles from a Von Mises distribution with mean mu and concentration k.
The Von Mises distribution has probability density functionf (x) = exp (k * cos (x - mu)) / Z ,
where Z is a normalisation constant.
The output, theta, is a matrix of size sz containing random angles drawn from the given Von Mises distribution. By default, mu is 0 and k is 1.See also: vmpdf