Sobel Edge detection Implementation Problem

I m new to MATLAB,Plz guide me.i m trying to implement the Sobel Edge detection algorithm but i m not getting correct output. My output is not match with the output obtained from using the inbuild edge function.This is my code. Thanks in advance.

gx=[-1 0 1;-2 0 2;-1 0 1];

d=conv2(original_Image,gx);

gy=[1 2 1;0 0 0;-1 -2 -1];

e=conv2(Original_Image,gy);

[m n]=size(e);

for i=1:m

for j=1:n

     G(i,j)=uint8(sqrt(d(i,j)*d(i,j)+e(i,j)*e(i,j)));

   end
end
figure;
imshow(G);