MATLAB: How to count the number of consecutive identical elements (in both the directions) in a binary vector

clusteringconsecutive numbervector

Suppose I have a binary vector

X = [0     0     0     0     1     1     1     0     1     1     1     1]

I want to characterize each element with the number of identical elements occurring in consecutive positions in both the directions. For instance, the desired output should look like:

Y = [4 4 4 4 3 3 3 1 4 4 4 4].

I found a similar thread, but it counts only in the forward direction. Thanks in advance for any sort of assistance.

Best Answer

With FEX: RunLength:

X      = [0     0     0     0     1     1     1     0     1     1     1     1];
[B, N] = RunLength(X);
Y      = RunLength(N, N);

If you do not have a C-compiler for the fast C-Mex function, use RunLength_M.

Or with Matlab code:

d = [true, diff(X) ~= 0, true];  % TRUE if values change
n = diff(find(d));               % Number of repetitions
Y = repelem(n, n)

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MATLAB: How to get the maximum consecutive NaNs for each column

Here you go:

result = zeros(1,size(A,2));
for i = 1:size(A,2)
    B = isnan(A(:,i));
    CC = bwconncomp(B);
    Sizes = cellfun(@length, CC.PixelIdxList);
    result(i) = max(Sizes);
end

MATLAB: Counting consecutive repeat values for each row in matrix

First, I would download Jan's RunLength utility from the File Exchange, which was designed to solve exactly this kind of problem.

X = [1 1 1 1 0 0 0 0 0 1 1 1 0 0 0 0;
     1 0 0 0 1 1 1 0 0 0 0 1 1 1 0 0];
for nr = 1:size(X,1)
    [b{nr} n{nr}] = RunLength(X(nr,:))
end

Each element of b will be the values of each consecutive "run", and n will have the lengths of those runs. So, in this example, the outputs are

% Row 1 results
[b{1}; n{1}]
ans =
     1     0     1     0
     4     5     3     4
     
     
% Row 2 results
[b{2}; n{2}]
ans =
     1     0     1     0     1     0
     1     3     3     4     3     2

You may need to do another step or two to get the output exactly as you want it, but this could be your first building block.

Best Answer

Related Solutions

MATLAB: How to get the maximum consecutive NaNs for each column

MATLAB: Counting consecutive repeat values for each row in matrix

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