function X=samples2mat
%convert image samples to matrix
%every image forms a row vector row after row
%in X,every row represents an image
X=[];
for i=1:40
    j=11:15
    a=imread(strcat('E:\ÅËÖ¾±ó\ÈËÁ³¿â\ORL\s,num2str(i),'\',num2str(j)''.pgm');
    [m,n]=size(a);
    b=[];
    for k=1:m
        b=[b,a(k,:)];
    end
    X=[X;b];
end