Fingerprint Image Orientation

I using Raymond Thai's Thesis to do Image orientation but some how i m not getting the desired output.
Can someone tell me if there is an error in the following code

I=double(N); %loading the normalised image
dx = blockproc(I,[ 16 16 ],@sample2); %sobel x-gradient
dy = blockproc(I,[ 16 16 ],@sample3); %sobel y-gradient
imview(I,[]);
imview(dx);
imview(dy);
save dx;
save dy;
[row , col]=size(dx);
vx=zeros(row,col);
vy=zeros(row,col);
theta=zeros(row,col);
phix=zeros(row,col);
phiy=zeros(row,col);
phidashx=zeros(row,col);
phidashy=zeros(row,col);
O=zeros(row,col);
for i=1:row
for j=1:col
for k=i-8:1:i+8
for l=j-8:1:j+8
if k>0 & k<=row & l>0 & l<=col
vx1=2*dx(k,l)*dy(k,l);
vx(i,j)=vx(i,j)+vx1;
vy1=dx(k,l)*dx(k,l)*dy(k,l)*dy(k,l);
vy(i,j)=vy(i,j)+vy1;
end
end
end
if vx(i,j)~=0
theta(i,j)=0.5*atan(vy(i,j)./vx(i,j));
end
phix(i,j)=cos(2*theta(i,j));
phiy(i,j)=sin(2*theta(i,j));
end
end
figure(4),imshow(vx);
figure(5),imshow(vy,[]);
figure(6),imshow(theta,[]);
figure(7),imshow(phix,[]);
figure(8),imshow(phiy,[]);
G = fspecial('gaussian',[16 16]);
for i=1:1:row
for j=1:1:col
for u=-8:1:8
for v=-8:1:8
if(u*16<i & v*16<j & i-16*u<=row & j-16*v<=col)
phidashx1=phix(i-u*16,j-v*16);
phidashy1=phiy(i-u*16,j-v*16);
end
if u>0 & v>0
phidashx1=G(u,v)*phidashx1;
phidashy1=G(u,v)*phidashy1;
phidashx(i,j)=phidashx(i,j)+phidashx1;
phidashy(i,j)=phidashy(i,j)+phidashy1;
end
end
end
if phidashx(i,j)~=0
O(i,j)=0.5*atan(phidashy(i,j)./phidashx(i,j));

end
end
end
imview(O);