load ('Data.mat');
train = images_train(:,1:3000);
train_l = labels_train(1:3000);
mat1 = find(train_l==1);
mat2 = find(train_l==7);
mat = [mat1',mat2']';
train_1_7 = train(:,mat);
Distance_mat = L2_distance(train_1_7,train_1_7);
[Y,R,E] = Isomap(Distance_mat,'k',7);