Parfor error - Error in ==> parallel_f​unction>ma​ke_general​_channel/c​hannel_gen​eral at 894 Index exceeds matrix dimensions.

I have the following code:

classes = {'1_NATURE';'2_SECONDARY_CLASS';'3_TERTIARY_CLASS'}

windows = {'None';'k3';'k5';'k7';'k9';'k11';'k13';'k15';'k17';'k19'};

str1 = 'D:\STUDY\A_IIT_MS_Project\MATLAB_RESULTS\SEQUENCE_PPT\ALL_AGAIN\';

str2 = '\Results\PPT'; str3 = '\Results\Response'; str4 = 'MLR_4_';

matlabpool open 4

parfor class = 1:size(classes,1)

addpath(strcat(str1,classes{class,1}));

    for window = 1:size(windows,1)  

            str_windows = strcat(windows{window,1},'_*');

            cd (strcat(str1,classes{class,1},str2)); 

            pre_list = struct([]); file_list = cell(zeros);

            pre_list = dir(str_windows); file_list = {pre_list.name}'; 

            cd (strcat(str1,classes{class,1},str3));

            pre_list1 = struct([]); file_list1 = cell(zeros);

            pre_list1 = dir('Response_*'); file_list1 = {pre_list1.name}';

              for list = 3:size(file_list,1)

                 input4 = file_list{list,1};
                 in_resp4 = file_list1{list,1};

                 concat = strcat(str4,input4);
                 after_concat = regexprep(concat,('.mat'),'');

                 output4 = after_concat;            

                 cd (strcat(str1,classes{class,1},str2));

                 Seq_num_prop_calc = cell(zeros);
                 Seq_num_prop_calc = load(input4); 

                cd (strcat(str1,classes{class,1},str3));
                variables = cell(zeros);
                variables = load(in_resp4);

    % Multiple Linear Regression 

        pre_y = 0; pre_x = 0;

        pre_y = cell2mat(variables(2:size(variables,1),1:7));
        pre_x = cell2mat(Seq_num_prop_calc(2:size(Seq_num_prop_calc,1),5:53));

        max_ppt = cell(zeros); count = 1;
        % 
        for god = 1:size(pre_y,2) % 7 Kf-Ku responses

            r_value = cell(zeros); a = 1; x1 = 0; x2 = 0; 
            y = pre_y(:,god);

            for i = 1:size(pre_x,2)

        for j = i+1:size(pre_x,2)          

                for k = j+1:size(pre_x,2)

                        for l = k+1:size(pre_x,2)                   

                                    x1 = pre_x(:,i);
                                    x2= pre_x(:,j);
                                    x3 = pre_x(:,k);
                                    x4 = pre_x(:,l);
                                    x = [x1,x2,x3,x4];

                                    x_1 = [x,ones(size(x(:,1)))];
                                    [b, bint, r, rint, stats] = regress(y,x_1);

                                    y_new = b(1)*x1 + b(2)*x2 + b(3)*x3 +b(4)*x4 + b(5);
                                    r_check = corr(y_new,y);

                                    god_response = variables{1,god};  ppt1 = Seq_num_prop_calc{1,i+4}; ppt2 = Seq_num_prop_calc{1,j+4}; 
                                    ppt3 = Seq_num_prop_calc{1,k+4}; ppt4 = Seq_num_prop_calc{1,l+4}; 
                                    o = (',');

                                    s = strcat(god_response,o,ppt1,o,ppt2,o,ppt3,o,ppt4);

                                    r_value(a,1) = {s}; 
                                    r_value(a,2) = {b};
                                    r_value(a,3) = {r_check};
                                    r_value(a,4) = {stats};
                                    a = a+1;
                        end
                end
        end
    end
            un_score = '_';
            class_name = strcat(output4,un_score,god_response);
            file_name = output4;

            r_value_mat = cell2mat(r_value(:,3));    
            max_id = find(r_value_mat == max(r_value_mat));

            if size(max_id,1) == 1 

                max_ppt(count,1) = {class_name}; 
                max_ppt(count+1,2:5) = r_value(max_id,1:4);
                count = size(max_ppt,1) + 1;

            elseif size(max_id,1) > 1 

                max_ppt(count,1) = {class_name}; 
                max_ppt(count+1:size(max_id,1),2:5) = r_value(max_id,1:4);
                count = size(max_ppt,1) + 1;

            end    
        end

        cd (strcat(str1,'MLR\MLR_Results\MLR_4'));
        savefunc (file_name, max_ppt, version)

        end
    end
end

matlabpool close

I am getting the following error:

??? Error using ==> parallel_function at 598 Error in ==> parallel_function>make_general_channel/channel_general at 894 Index exceeds matrix dimensions.

Error in ==> MLR_4 at 13 parfor class = 1:size(classes,1)

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

[Walter Roberson]

Have you tried using a regular "for" and seeing if it works that way?