How can I find run length consecutive ones and zeros and their occurrence times in a binary sequence in MATLAB?

I would like to find run length of consecutive ones and zeros in a binary sequence and the number of times each length occurs.

Answer 1

[MathWorks Support Team]

You can use the TEXTSCAN function by specifying delimiters and then use LENGTH function to find the length of each sequence. After that, you can compute the number of occurrences with HIST function as in the example below:

%Creating a binary sequence in a string with no spaces 

s = [1 1 0 0 0 0 0 1 1 1 1 0 1 1 0 1 1 0 1 1 1 0 1 0 1 0 1 0 0 1 1 1];

s = sprintf('%d',s);

%Reading the consequences of 1's from the string by using 0's as delimiters

t1=textscan(s,'%s','delimiter','1','multipleDelimsAsOne',1);

% Converting cell array of cell into a single cell array

d = t1{:};

% Computing the length of each run by going through the array and assigning

% it into 

for k = 1:length(d)

      data(k) = length(d{k});

end

% Using histogram function to compute the number of times for each length

[number_times run_length] = hist(data, [1:max(data)])

To do the same operation for finding run lengths and frequencies of "zeros" instead of "'ones", change the delimiter in the TEXTSCAN function to be '1' instead of '0'.

[Jan]

The loop for k = 1:length(d), data(k) = length(d{k}); end can be replaced by the more efficient:

data = cellfun('length', d);

Answer 2

[Jan]

With FEX: RunLength:

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

Or with M-code:

d = [true; diff(s(:)) ~= 0];   % TRUE if values change
B = x(d);                      % Elements without repetitions
k = find([d', true]);          % Indices of changes
N = diff(k);                   % Number of repetitions

Now B is the value and N the number of repetitions.

This is easier and more efficient than converting the data to a string, running textscan and counting the length of the output in a loop.

[Image Analyst]

I think he meant s, not x