Error using fread and imageparser - matlab

Question

Hello when l run the code above l got this error . l don't where is the error ,my codes (.m) and training examples are in the same working directory.
Error using fread
Invalid file identifier. Use fopen to generate a valid file identifier.
Error in MNISTParser (line 3)
magic_number = fread(fp,1,'uint32',0,'b');
Error in MNIST_gen (line 2)
train_labels = MNISTParser('./MNIST/train-labels-idx1-ubyte');
MNIST_gen.m
clear
**train_labels = MNISTParser('./MNIST/train-labels-idx1-ubyte');**
train_images = MNISTParser('./MNIST/train-images-idx3-ubyte');
test_labels = MNISTParser('./MNIST/t10k-labels-idx1-ubyte');
test_images = MNISTParser('./MNIST/t10k-images-idx3-ubyte');
test_item_number = length(test_labels);
train_item_number = length(train_labels);
image_scale = size(test_images,2);
test_images_unfold = reshape(test_images,test_item_number,image_scale^2)';
test_labels_unfold = full(ind2vec(test_labels'+1));
train_images_unfold = reshape(train_images,train_item_number,image_scale^2)';
train_labels_unfold = full(ind2vec(train_labels'+1));
save MNIST.mat;
colormap(gray);
axis off
axis image
%show an image of a digit in test samples
for i=1:1
j=randi(length(test_labels),1);
image(reshape(255-test_images(j,:,:),28,28));
title(sprintf('%d',test_labels(j)));
pause(1);
image(reshape(test_images_unfold(:,j),28,28));
title(vec2ind(test_labels_unfold(:,j))-1);
pause(1);
end
%show an image of a digit in train samples
for i=1:1
j=randi(length(train_labels),1);
image(reshape(255-train_images(j,:,:),28,28));
title(sprintf('%d',train_labels(j)));
pause(1);
image(reshape(train_images_unfold(:,j),28,28));
title(vec2ind(train_labels_unfold(:,j))-1);
pause(1);
end
MNISTParser.m
function res = MNISTParser(filename)
fp = fopen(filename,'r');
**magic_number = fread(fp,1,'uint32',0,'b');**
items_number = fread(fp,1,'uint32',0,'b');
if 2049==magic_number
res = fread(fp,items_number,'uint8',0,'b');
else
if 2051==magic_number
img_rows = fread(fp,1,'uint32',0,'b');
img_cols = fread(fp,1,'uint32',0,'b');
res = zeros(items_number,img_rows,img_cols);
for i=1:items_number
res(i,:,:) = fread(fp,[img_cols,img_rows],'uint8',0,'b')';
end
else
error('wrong magic number');
end
end
fclose(fp);
end
Thanks for helps

Answer 1

l find the mistake. it is related to the extension of the files.
here is the instruction that has helped me to find out my mistake [fp,msg] = fopen(filename,'r');
if fp<1, error([msg ' File: ' filename]);