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_Ncdf_jdw.m
    path of file: ./repos/bspm/thirdparty/spm12
    
    the code of the file until where you have to start completion: function F = spm_Ncdf_jdw(x,u,v)
% Cumulative Distribution Function (CDF) for univariate Normal distributions: J.D.  Williams aproximation
% FORMAT F = spm_Ncdf_jdw(x,u,v)

    
function F = spm_Ncdf_jdw(x,u,v)
% Cumulative Distribution Function (CDF) for univariate Normal distributions: J.D.  Williams aproximation
% FORMAT F = spm_Ncdf_jdw(x,u,v)
%
% x - ordinates
% u - mean              [Defaults to 0]
% v - variance  (v>0)   [Defaults to 1]
% F - pdf of N(u,v) at x (Lower tail probability)
%__________________________________________________________________________
%
% spm_Ncdf implements the Cumulative Distribution Function (CDF) for
% the Normal (Gaussian) family of distributions.
%
% References:
%--------------------------------------------------------------------------
% An Approximation to the Probability Integral
% J. D. Williams 
% The Annals of Mathematical Statistics, Vol. 17, No. 3. (Sep., 1946), pp.
% 363-365. 
%
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

% Karl Friston
% $Id: spm_Ncdf_jdw.m 4836 2012-08-10 15:55:21Z karl $


%-Format arguments
%--------------------------------------------------------------------------
if nargin < 3, v = 1; end