Rayleigh cumulative distribution function
p = raylcdf(x,b)
p = raylcdf(x,b,'upper')
p = raylcdf(x,b) returns the Rayleigh cdf at each value in x using the corresponding scale parameter, b. x and b can be vectors, matrices, or multidimensional arrays that all have the same size. A scalar input for x or b is expanded to a constant array with the same dimensions as the other input.
p = raylcdf(x,b,'upper') returns the complement of the Rayleigh cdf at each value in x, using an algorithm that more accurately computes the extreme upper tail probabilities.
The Rayleigh cdf is
 Evans, M., N. Hastings, and B. Peacock. Statistical Distributions. Hoboken, NJ: Wiley-Interscience, 2000. pp. 134–136.