How to find the neighbors of each element in a matrix

Hi,

how I can find the neighbors of each element in a given matrix? Does such a method exist in Matlab?

Here is an example : A=[3 4 8 6; 1 6 9 0; 2 5 7 1]

The neighbors of A(1,1) are {1, 4, 6}; The neighbors of A(1,2) are {3, 1, 6, 8, 9}; The neighbors of A(2, 1) are {3, 2, 4, 6, 5}; The neighbors of A(2, 2) are {3, 1, 2, 4, 5, 8, 9, 7}

Thanks.

[Mitulkumar Vasani]

i have quation regarding finde neighbors for vector

ex. A=[-20 -15 -12 -10 -5 - 3 0 1 2 5 6 8 10]

if i need a to find nearest neighbors for (3)

then as answer will come as 2 and 5

is there any code in matlab?

Answer 1

[Stephen23]

Here is a simple method using conv2:

>> A = [3,4,8,6;1,6,9,0;2,5,7,1];
>> M = zeros(size(A));
>> M(1,1) = 1; % location
>> A(conv2(M,[1,1,1;1,0,1;1,1,1],'same')>0)
ans =
   1
   4
   6
>> M(:) = 0;
>> M(1,2) = 1; % location
>> A(conv2(M,[1,1,1;1,0,1;1,1,1],'same')>0)
ans =
   3
   1
   6
   8
   9
>> M(:) = 0;
>> M(2,1) = 1; % location
>> A(conv2(M,[1,1,1;1,0,1;1,1,1],'same')>0)
ans =
   3
   2
   4
   6
   5
>> M(:) = 0;
>> M(2,2) = 1; % location
>> A(conv2(M,[1,1,1;1,0,1;1,1,1],'same')>0)
ans =
   3
   1
   2
   4
   5
   8
   9
   7

[Emerson Nascimento]

IT WAS AMAZING !

[Dyuman Joshi]

I have accepted Stephen's answer as it solves the problem with clarity.

Answer 2

[Andrei Bobrov]

s = size(A);
B = zeros(s);
n = numel(A);
out = cell(s);
for ii = 1:n
  B(ii) = 1;
  out{ii} = A(bwdist(B,'ch') == 1);
  B(ii) = 0;
end

Answer 3

[KSSV]

IT can be very much done....you may refer this link: https://in.mathworks.com/matlabcentral/answers/10293-finding-neighbor-of-a-position