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copied!<p>The first step would be to create a function that can generate an n-gram for a given string. One way to do this in a vectorized fashion is with some clever indexing.</p> <pre><code>function [subStrings, counts] = n_gram(fullString, N) if (N == 1) [subStrings, ~, index] = unique(cellstr(fullString.')); %.'# Simple case else nString = numel(fullString); index = hankel(1:(nString-N+1), (nString-N+1):nString); [subStrings, ~, index] = unique(cellstr(fullString(index))); end counts = accumarray(index, 1); end </code></pre> <p>This uses the function <a href="http://www.mathworks.com/help/techdoc/ref/hankel.html" rel="nofollow noreferrer">HANKEL</a> to first create a matrix of indices that will select each set of unique N-length substrings from the given string. Indexing the given string with this index matrix will create a character array with one N-length substring per row. The function <a href="http://www.mathworks.com/help/techdoc/ref/cellstr.html" rel="nofollow noreferrer">CELLSTR</a> then places each row of the character array into a cell of a cell array. The function <a href="http://www.mathworks.com/help/techdoc/ref/unique.html" rel="nofollow noreferrer">UNIQUE</a> then removes repeated substrings, and the function <a href="http://www.mathworks.com/help/techdoc/ref/accumarray.html" rel="nofollow noreferrer">ACCUMARRAY</a> is used to count the occurrences of each unique substring (if they are needed for any reason).</p> <p>With the above function you can then easily count the number of n-grams shared between two strings using the <a href="http://www.mathworks.com/help/techdoc/ref/intersect.html" rel="nofollow noreferrer">INTERSECT</a> function:</p> <pre><code>subStrings1 = n_gram('tool',2); subStrings2 = n_gram('fool',2); sharedStrings = intersect(subStrings1,subStrings2); nShared = numel(sharedStrings); </code></pre>

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