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: CBIG_MM_KRR_classical_split_subject.m
    path of file: ./repos/CBIG/stable_projects/predict_phenotypes/He2022_MM/KRR_CLASSICAL
    
    the code of the file until where you have to start completion: function CBIG_MM_KRR_classical_split_subject(data_dir, subject_list_file, rng_num, k, y, pre_fix)

% CBIG_MM_KRR_classical_split_subject(data_dir, subject_list_file, rng_num, k, y, pre_fix)
% 
% This function splits subjects into k subjects and remaining subjects.
%
% Inputs:
%   - data_dir
%     Path of the your output and intermediate values. You can
%     also change this to any place you want.
%   - subject_list_file
%     Path of subject list of setup_file dataset. It should be a txt file
%     that contains #subject of line, while each line is the subject id of
%   - rng_num
%     Number (integer) of random number generator
%   - k
%     Number (integer) of the K for K shot (participants) learning
%   - y
%     array of y, phenotype value
%   - pre_fix
%     name pre fix for the split file saving
% 
% Written by Tong He and CBIG under MIT license: https://github.com/ThomasYeoLab/CBIG/blob/master/LICENSE.md

rng(rng_num);

% read out subject file
fileID = fopen(subject_list_file);
temp = textscan(fileID, '%d');
subject_list = temp{1};

% Train/Validation/Test split
num_total = size(subject_list, 1);

    
function CBIG_MM_KRR_classical_split_subject(data_dir, subject_list_file, rng_num, k, y, pre_fix)

% CBIG_MM_KRR_classical_split_subject(data_dir, subject_list_file, rng_num, k, y, pre_fix)
% 
% This function splits subjects into k subjects and remaining subjects.
%
% Inputs:
%   - data_dir
%     Path of the your output and intermediate values. You can
%     also change this to any place you want.
%   - subject_list_file
%     Path of subject list of setup_file dataset. It should be a txt file
%     that contains #subject of line, while each line is the subject id of
%   - rng_num
%     Number (integer) of random number generator
%   - k
%     Number (integer) of the K for K shot (participants) learning
%   - y
%     array of y, phenotype value
%   - pre_fix
%     name pre fix for the split file saving
% 
% Written by Tong He and CBIG under MIT license: https://github.com/ThomasYeoLab/CBIG/blob/master/LICENSE.md

rng(rng_num);

% read out subject file
fileID = fopen(subject_list_file);
temp = textscan(fileID, '%d');
subject_list = temp{1};

% Train/Validation/Test split
num_total = size(subject_list, 1);
num_train = k;
num_test = num_total - num_train;

% handle missing value
ind_real = ~isnan(y);
num_real = sum(ind_real);
if num_total ~= k
    % dont check if num_total is K for intentional usage
    if num_real < 1.5 * k
        error([num2str(num_real) ' is less than 1.5 * ' num2str(k)])
    end