it does nothing to handle cases where |NaN|s might be involved.it was only written to work on vectors,.it is not as general purpose and does no error checking,.Some possible reasons why findPattern2 is the fastest of the three algorithms: MATLAB provides functions and GUIs to perform a variety of common data-analysis tasks, such as plotting data, computing descriptive statistics, and performing linear correlation analysis, data fitting, and Fourier analysis. In the case of the larger dataset, strfind is not the fastest algorithm, though I found with much smaller data, strfind outperformed findPattern2. Tfind(3) = timeit(f) Name Size Bytes Class Attributes Now let me show and time finding the pattern in the raw data. Let me show you one of the images in the sequence, after processing The images are separated by a particular bit pattern. He has a file with multiple images in it, with data stored as uint8. Jeff described the problem he was solving in more detail. Despite its name, strfind can happily handle non-character datatypes, and particularly doubles and integers. Next I test using the same data with strfind. Locs = pattern(pattval) = array(start+pattval-1) % array, to check which possible locations are valid still. % Next, loop over elements of pattern, usually much shorter than length of % Next remove start values that are too close to the end to possibly match % First, find candidate locations i.e., match the first element in the % For this algorithm, I loop over the pattern elements. % VECTORS, but there's no checking for this. % Let's assume for now that both the pattern and the array are non-empty % indices = findPattern2(array, pattern) finds the starting indices of %findPattern2 Locate a pattern in an array. The idea here is to find possible pattern locations first, and winnow them out, marching through the pattern, which I am assuming is generally smaller, and often a lot smaller, than the data.įunction start = findPattern2(array, pattern) MATLAB FIND CODEThen I can reuse the same code for the other cases simply by redefining First I set f to be a function handle to the function in question. You'll notice that Jeff chooses to store derived information on the pattern being present in a cell array, and then looks % pattern matches many positions in the array. % with more than half a dozen elements where the first element in the % As currently implemented, this routine has poor performance for patterns % of consecutive integers in consecutive cells. % When the pattern exists in the input stream, there will be a sequence % i-th cell contains the positions in the input array that match the i-th % For an n element pattern, the result is an n element cell array. % Find all of the occurrences of each number of the pattern. % See also STRFIND, STRCMP, STRNCMP, STRMATCH. % can be any mixture of character and numeric types. % of any occurences of the PATTERN in the ARRAY. % K = FINDPATTERN(ARRAY, PATTERN) returns the starting indices a = ī = double( 'The year is 2003.') First Algorithm : findpatternįunction idx = findpattern(in_array, pattern) Let me start off with really simple test data to be sure all algorithms are getting the right answers.
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