Draws samples in [0, 1] from a power distribution with positive exponent a  1.
Also known as the power function distribution.
Parameters:  a : float
size : tuple of ints


Returns:  samples : {ndarray, scalar}

Raises:  ValueError :

Notes
The probability density function is
The power function distribution is just the inverse of the Pareto distribution. It may also be seen as a special case of the Beta distribution.
It is used, for example, in modeling the overreporting of insurance claims.
References
[R250]  Christian Kleiber, Samuel Kotz, “Statistical size distributions in economics and actuarial sciences”, Wiley, 2003. 
[R251]  Heckert, N. A. and Filliben, James J. (2003). NIST Handbook 148: Dataplot Reference Manual, Volume 2: Let Subcommands and Library Functions”, National Institute of Standards and Technology Handbook Series, June 2003. http://www.itl.nist.gov/div898/software/dataplot/refman2/auxillar/powpdf.pdf 
Examples