while using for loop in following function some blank cells are come into output matrix like [ ] [ ] [ ]. I dont understand where i wrong in for loop

function build_db(ICount, JCount)
    p=0;
    path = 'E:\MATLAB\R2016b\bin\img\PCA\my_PhD_Programs\minuite\FVC2002\DB1_B\'
    for i=1:ICount           % 10
        for j=1:JCount    % 8
            filename=[path,num2str(i) '_' num2str(j) '.bmp'];      
            img = imread(filename); 
            img =  imresize(img,[374 388]);
            p=p+1;
            if ndims(img) == 3;
                img = rgb2gray(img);
            end   % colour image
            disp(['extracting features from ' filename ' ...']);
            if j<4
                testdata{p}=ext_vein(img,1);
            else
                traindata{p}=ext_vein(img,1);        
           end
        end
    end      
    save('db1.mat','testdata');
    save('db2.mat','traindata');
end

%********************************************** Function invoked *******************

build_db(2,8);                                                  %THIS WILL TAKE ABOUT 30 MINUTES

   load('db1.mat');
   load('db2.mat');

testdata = testdata';                                              % Adjust matrix dimension
testfeature = cell2mat(testdata);                           % Convert cell array to matrix
traindata = traindata';
trainfeature = cell2mat(traindata);

dist = pdist2(testfeature,trainfeature,'euclidean');        % compute euclidian distance

%*****************************************OUTPUT We Get *********************************************** Testdata matrix contains following values

54x6 double
44x6 double
44x6 double
[]
[]
[]
[]
[]
44x6 double
60x6 double
38x6 double

and traindata contains following values

[]
[]
[]
50x6 double
47x6 double
38x6 double
31x6 double
43x6 double
[]
[]
[]
35x6 double
37x6 double
39x6 double
27x6 double
27x6 double

Answer 1

[Stephen23]

You use the variable p as an index into both the training and test data cell arrays, so when you have incremented the training data index it clearly also increments the test index, because it is the same index!

The solution is simple: replace p with two separate indices, and increment them independently:

id_test = 0;
id_train = 0;
for ...
    for ...
        ...
        if j<4
            id_test = id_test+1;
            testdata{id_test} = ...;
        else
            id_train = id_train+1;
            traindata{id_train} = ...;        
       end
       ...
   end
end

[Balaji M. Sontakke]

Thank you sir..

Answer 2

[wisam kh]

Hello when I try this code I got this error

Error in build_db (line 9) img = imread(filename);

how can I solve it, help me please

[Stephen23]

@wisam kh: please give the complete error message. This means all of the red text.