function[r,t]=rect_to_polar(x,y)
r=sqrt(x*x+y*y);
if (x==0) 
if (y>0)
t=3.15159/2;
elseif (y < 0)
t=3*3.15159/2;
else
t=0;
end
else
t=atan(y/x);
end
if x>0 & y>0
elseif x>0 & y<0 
t=t+2*3.15159;
elseif x<0 & y>0
t=t+3.15159;
elseif x<0 & y<0
t=t+3.15159;
end
