Problem in sobel edge detection method

I need to make a sobel edge detection. I shouldn't use the shortcuts of MATLAB functions. I couldn't run the code and i can't find my error. I get a white screen as a output. I think that i didn't make the non maximum suppression so i get the error. Thanks for helping

orginal=imread('img.jpg');
orgdoub=im2double(orginal);

gray_img=rgb2gray(orgdoub);

kx=[-100,-200,-100;0 0 0 ; 100 200 100];
ky=[-100 0 100; -200 0 200 ; -100 0 100];

H= conv2(gray_img,kx,'same');
V= conv2(gray_img, ky, 'same');

E=sqrt(H.^2+V.^2);

filterimg=imfilter(gray_img,E);
edgeimg=edge(filterimg);
figure(1);
imshow(filterimg);
title('gradyantlı');

figure(2);
sob = edge(gray_img,'sobel');
imshow(sob);
title('With using sobel function ');