Neighbor searching

Hello!

I have a meshgrid created like this:

x=1:10; y=1:10; [X Y]=meshgrid(x,y);

X =

     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10
     1     2     3     4     5     6     7     8     9    10

and

Y =

     1     1     1     1     1     1     1     1     1     1
     2     2     2     2     2     2     2     2     2     2
     3     3     3     3     3     3     3     3     3     3
     4     4     4     4     4     4     4     4     4     4
     5     5     5     5     5     5     5     5     5     5
     6     6     6     6     6     6     6     6     6     6
     7     7     7     7     7     7     7     7     7     7
     8     8     8     8     8     8     8     8     8     8
     9     9     9     9     9     9     9     9     9     9
    10    10    10    10    10    10    10    10    10    10

I would like to implement a neighbor searching as follow: - select one position (X=4,Y=5) - obtain as output the coordinates of the points close to the previous one; in the case of a matrix (for example) 1X1 this would be: 1) X=3 Y=4 2) X=4 Y=4 3) X=5 Y=4 4) X=3 Y=5 5) X=5 Y=5 6) X=3 Y=6 7) X=4 Y=6 8) X=5 Y=6

Is there any function that does that in matlab ?

Answer 1

[Andrei Bobrov]

I = zeros(10);
x = 4;
y = 5;
I(x,y) = 1;
[yout,xout] = find((bwdist(I,'chessboard') == 1)');

variant 2

x=1:10;
y=1:10;
[X Y]=meshgrid(x,y);
i1 = 4;
j1 = 5;
[yout,xout] = find(max(abs(X-i1),abs(Y-j1))' == 1);

Answer 2

[Sean de Wolski]

Or:

sz = 10;
I = false(sz);
I(4,5) = true; %point we care about
[row col] = find(imdilate(I,true(3)))