MatLab - Ring Area

function [ring_area] = my_ring(r,R)

ring_area = 0 ;

fileID = fopenn('duck.txt', 'w');
fprintf(fileID, '%f\n',r);
fprintf(fileID, '%f\n','-');
fprintf(fileID, '%f\n',R);
fprintf(fileID, '%f\n','--');
fclose(fileID);


if norm(r)>0 & norm(R)>0 & norm(R)>norm(r) & size(r) == size(R)
    ring_area = pi * (norm(R).^2 - norm(r).^2) ;
else
    ring_area = -1 ;
end