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_mvb_p.m
    path of file: ./repos/spm12
    
    the code of the file until where you have to start completion: function [p] = spm_mvb_p(MVB,k)
% Classical p-value for MVB using null distribution of log-odds ratio

    
function [p] = spm_mvb_p(MVB,k)
% Classical p-value for MVB using null distribution of log-odds ratio
% FORMAT [p] = spm_mvb_p(MVB,k)
%
% MVB - Multivariate Bayes structure
% k   - number of samples > 20
%
% p   - p-value: of (relative) F using an empirical null distribution
%
% spm_mvb_p evaluates an empirical null distribution for the (fee-energy)
% difference in log-evidences (the log odds ratio) by phase-shuffling the
% target vector and repeating the greedy search. It adds the p-value as a
% field (p_value) to MVB.
%__________________________________________________________________________
% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging
 
% Karl Friston
% $Id: spm_mvb_p.m 4492 2011-09-16 12:11:09Z guillaume $
 
%-number of samples
%--------------------------------------------------------------------------
try
    k;
catch
    str   = 'number of samples for null distribution';
    k     = spm_input(str,'!+1','b',{'20','50','100'},[20 50 100]);
end