A distribution used to model spherical data. The probability density function f in the direction (θ, Φ) is given bywhere c is a positive constant and the non-negative parameter κ is a measure of the concentration of the distribution, which is symmetrical about the mode. The case κ=0 corresponds to a uniform distribution over the entire sphere. If κ≠0 the distribution has mode at (θ₀, Φ₀).