function HX = mhalf(X, side)

s = size(X);

if side == 'up'
    sr = round(s(2)/2);
    HX = X(:,1:sr);
elseif side == 'down'
    sr = round(s(2)/2);
    HX = X(:,sr:s(2));
elseif side == 'left'
    sr = round(s(1)/d);
    HX = X(1:sr,:);
elseif side == 'right'
    sr = round(s(1)/d);
    HX = X(sr:s(1),:);
end