Find continuous elements in matrix

Hi everyone,

my problem is the following: i've one matrix made of two possible values (i.e. 1 and 0). I also have the coordinates of one "starting point". I would like to select all the ones that are connected to this point without selecting the ones that are separeted by zeros. I can't figure out a way to solve the problem... can you help me?

Thanks in advance, Fabio

[Walter Roberson]

Do you have the Image Processing Toolbox?

Answer 1

[Andrei Bobrov]

use functions bwlabel and regionprops from Image Processing Toolbox

eg

youridx = {10,6}; % coordinates of one "starting point" (row - 10, column - 6)

a = [...
     0     0     0     0     0     0     0     0     0     0
     0     1     0     0     0     0     0     0     0     0
     0     0     1     0     0     0     0     0     0     1
     0     1     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     1     0     0     1     0
     0     0     1     0     1     0     0     1     0     0
     0     1     0     0     0     0     0     0     1     0
     0     0     1     0     0     0     0     1     0     0
     0     0     0     0     1     1     1     0     0     0];

S = regionprops(a~=0,'PixelList');
t = bwlabel(a);
out =  = fliplr(S(t(idx{:})).PixelList);

[Fabio]

Thank you very much, this is working very well! I didn't mention in my introduction that the matrix i'm looking at is a 3d matrix (or it could be in future applications a n-dimension matrix, with n>3), but hopefully i'll find a way to extend this code to the 3rd dimension. If you have any other suggestion please tell me.

[Sean de Wolski]

should be extendable as is.

Answer 2

[Sean de Wolski]

CC = bwconncomp(a); 
CC.PixelIdxList{:}