function F = spm_Xcdf(x,v)
% Cumulative Distribution Function (CDF) of Chi-squared distribution
% FORMAT F = spm_Xcdf(x,v)
%
% x - Chi-squared variate
% v - degrees of freedom (v>0, non-integer d.f. accepted)
% F - CDF at x of Chi-squared distribution with v degrees of freedom
%__________________________________________________________________________
%
% spm_Xcdf implements the Cumulative Distribution of Chi-squared
% distributions.
%
% Returns the probability p, that a Students Chi-squared variate on v
% degrees of freedom is less than x. F(x) = Pr{X