Unable to replace values in a matrix

Question

I'm currently working on a cellular automata but i keep running into this problem. I have a matrix idxR which contains zero's and/or ones, depending on a probability process:

idxR = ((rRecr>rEmpty)&(rRecr>rAlgae)&(rRecr>rCoral));

Now i want to replace all ones in idxR with unique values and assign it to the variable colonies. I came up with the following:

colonies = idxR; 
no = sum(colonies(:)==1)
maxvalue = max(colonies(:));
replace = [1:no]+maxvalue;
ret = reshape(replace,no,1);
colonies(colonies==1) = colonies(colonies==1).*ret;

When i output colonies it gives me a matrix with just ones and zeros and not a matrix where all ones have been replaced with incremental values. I tried this code in a new file and assigned a matrix with random ones and zeros to idxR and then it seems to work. So i guess to problem lies with the matrix idxR in my automata. It might be worth mentioning that idxR is contained in a for loop.

Can somebody tell me how to fix this?

Answer 1

You got the entire logic correct, except one minor flaw. You have idxR as a logical matrix. Hence colonies is a logical matrix too. Therefore, you get the expected output till the second-last line. Problem occurs on the last line, when you try to assign an array of numbers in which each number is greater than 1 (colonies(colonies==1).*ret;) to a logical matrix.

Elements greater than 1 are clipped to one and thus you see only zeros and ones. There is a simple workaround. Change the first line to

colonies = double(idxR);

P.S. The answer was right in front of you, you just didn't spot it. You had written:

I tried this code in a new file and assigned a matrix with random ones and zeros to idxR and then it seems to work.

The idxR matrix must have been of double datatype, if you used randi.

Answer 2

Parag got it right. You have the solution there.

You can use the following code if you are looking for a more "organized" way to get to 'colonies' -

colonies = double(idxR);
maxvalue = max(colonies(:));
ind1 = find(idxR==1);
colonies(ind1)=maxvalue + (1:numel(ind1));