You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: spm_Xcdf.m
    path of file: ./repos/bspm/thirdparty/spm12
    
    the code of the file until where you have to start completion: function F = spm_Xcdf(x,v)
% Cumulative Distribution Function (CDF) of Chi-squared distribution
% FORMAT F = spm_Xcdf(x,v)

    
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<x} for X~\Chi^2(v)
%
% Definition:
%--------------------------------------------------------------------------
% The Chi-squared distribution with v degrees of freedom is defined for
% positive integer v and x in [0,Inf). The Cumulative Distribution
% Function (CDF) F(x) is the probability that a realisation of a
% Chi-squared random variable X has value less than x. F(x)=Pr{X<x}:
% (See Evans et al., Ch8)
%
% Variate relationships: (Evans et al., Ch8 & Ch18)
%--------------------------------------------------------------------------
% The Chi-squared distribution with v degrees of freedom is equivalent to
% the Gamma distribution with scale parameter 1/2 and shape parameter v/2.
%
% Algorithm:
%--------------------------------------------------------------------------
% Using routine spm_Gcdf for Gamma distribution, with appropriate parameters.
%
% References:
%--------------------------------------------------------------------------
% Evans M, Hastings N, Peacock B (1993)
%       "Statistical Distributions"
%        2nd Ed. Wiley, New York
%
% Abramowitz M, Stegun IA, (1964)
%       "Handbook of Mathematical Functions"
%        US Government Printing Office
%
% Press WH, Teukolsky SA, Vetterling AT, Flannery BP (1992)
%       "Numerical Recipes in C"
%        Cambridge
%
%__________________________________________________________________________
% Copyright (C) 1992-2011 Wellcome Trust Centre for Neuroimaging

% Andrew Holmes
% $Id: spm_Xcdf.m 4182 2011-02-01 12:29:09Z guillaume $


%-Check enough arguments
%--------------------------------------------------------------------------
if nargin<2, error('Insufficient arguments'), end