# Finding a specific pattern in data

14 views (last 30 days)
Ricardo Duarte on 10 Nov 2023
Commented: Ricardo Duarte on 15 Nov 2023
Hello all,
I would like to create a routine to identity if a specifi pattern exists in may data.
So far I did this:
data=somematrix;
% Define the pattern to search for
pattern = [3, 4, 5];
% Initialize a flag to check if the pattern is found
patternFound = false;
% Iterate through the data with a sliding window
for i = 1:(length(data) - length(pattern) + 1)
% Extract a subsequence of the same length as the pattern
subsequence = data(i:i+length(pattern)-1);
% Compare the subsequence with the pattern
if isequal(subsequence, pattern)
patternFound = true;
break; % Exit the loop if the pattern is found
end
end
% Display the result
if patternFound
disp('Pattern Found in the Data.');
else
end
This works when the data is a vector but is not working if instead a vector I'm working with a matrix.
Dyuman Joshi on 10 Nov 2023
How should the pattern be detected in the matrix?
Horizontally? Vertically? Diagonally? Or reverse of the orientations mentioned?

Johnny on 10 Nov 2023
Hello Ricardo,
You can use the ismember function (https://www.mathworks.com/help/matlab/ref/double.ismember.html) combined with logical operations.
patternFound = false ;
% Check if pattern is a subset of data
if size(data,2) < size(pattern,2)
% pattern cannot be found: column number in pattern is greater than column number in data
patternFound = false ;
elseif size(data,2) == size(pattern,2)
% Same number of column between pattern and data
patternFound = all(ismember(pattern, data, 'rows'));
else
% column number in data is greater than column number in pattern
% Extract submatrices from data, to have the same number of columns
% for comparison and loop through the different combinations.
for k = 1:(size(data,2)-size(pattern,2)+1)
patternFound = all(ismember(pattern, data(:, k:(k+size(pattern, 2)-1)), 'rows'));
if patternFound
break
end
end
end
%
if patternFound
disp('Pattern Found in the Data.');
else
end
Dyuman Joshi on 15 Nov 2023
@Ricardo Duarte, see the below example -
arr = [3 4 6
4 4 6
5 6 5];
pattern = [3 4 5];
In the array, the pattern is found - but vertically and diagonally, which is not the same the orientation as of the pattern, that is horizontal.
So, here, should the pattern be considered to be found, or not?
Ricardo Duarte on 15 Nov 2023
Thank you both @Johnny and @Dyuman Joshi,
The purpose is to find the pattern of a biological signal which is kind as wave. So in this case I think that diagonally could be the best option.
Thank you

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