function pol = pol(x,y)
%pol(x,y) for x and y column vectors
r = sqrt(x.^2 + y.^2);
for I = 1 : length(x),
if(x(I)>0)
    theta(I) = atan(y(I)/x(I));
elseif(x(I)<0)
    if(y(I)>0)
        theta(I) = atan(y(I)/x(I)) + pi;
    elseif(y(I)<0)
        theta(I) = atan(y(I)/x(I)) - pi;
    else
        theta(I) = pi;
    end
else
    if(y(I)>0)
        theta(I) = pi / 2;
    elseif(y(I)<0)
        theta(I) = -pi/2;
    else
        theta(I) = 0;
    end
end
end
x=x';
y=y';
r=r';
M=[x;y;r;theta]';
label={'x','y','r','Theta'};

fprintf('      x         y          r      Theta\n')
disp(M)

end