I've been studying to smoothing image with average of k- nearest neighbor filter.Here my code,but it has something wrong. Please help me or give me code for this algorithm? Many thanks...

I=uigetfile({'*.jpg';'*.png';'*.tif';'*.bmp'},'Select Image');
Img=imread(I);
a = rgb2gray(Img);
figure, imshow(a)
an=imnoise(a,'gaussian');
[m,n]=size(an);
figure, imshow(uint8(an))
b=input('Enter Averaging Mask size: ');
z=ones(b); 
[p,q]=size(z); 

w=1:p;
x=round(median(w));
anz=zeros(m+2*(x-1),n+2*(x-1));

for i=x:(m+(x-1))
    for j=x:(n+(x-1))
        anz(i,j)=an(i-(x-1),j-(x-1));
    end
end
figure, imshow(uint8(anz))
% tính điểm ảnh trung bình
k=input('Enter k value:');
E = zeros(1, b*b);
sum=0;
w =1;
for i=1:m
    for j=1:n
        for x=1:p
            for l=1:q 
               E(1,w)= anz(x,l);
               w = w + 1;
            end
        end
            for y=1:k
              A = sort(E,'descend');
              sum = sum + A(1,y);
              T = sum/k;
              an(i,j) = T;
            end         
    end
end
figure, imshow(uint8(anz));