function angle = arotHR(mx,my,j) %Unit vectors

i = 1;
% j è la data
if my(i,j)>0
    angle = 90-(atan(mx(i,j)/my(i,j)))*180/pi;
elseif my(i,j)<0 
    angle = 270-(atan(mx(i,j)/my(i,j)))*180/pi;
elseif (my(i,j)==0)&&(mx(i,j)<0) 
    angle = 180.0;
elseif (my(i,j)==0)&&(mx(i,j)>0)
    angle = 0.0;
end

end