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    <p>Let's solve this step by step: I'm assuming <code>FIT_txt</code> is a <code>Nx1</code> cell array and <code>sector</code> is a <code>Mx1</code> cell array.</p> <p>First find the rows in FIT_txt where <code>sector(ii)</code> appears in, and also how many times:</p> <pre><code>ii=1; sector_occurrence = strfind(FIT_txt,sector(ii)); </code></pre> <p>This gives you <code>N</code> cells for each row of FIT_txt with in each cell the actual location at each row where <code>sector(ii)</code> is found. You just need the count per row, so use <a href="http://www.mathworks.nl/help/techdoc/ref/numel.html" rel="nofollow">numel</a> to get just that:</p> <pre><code>cellfun(@numel,sector_occurrence ); </code></pre> <p>You can do this for every element of <code>sector</code> with a loop or with <a href="http://www.mathworks.nl/help/techdoc/ref/arrayfun.html" rel="nofollow">arrayfun</a>:</p> <pre><code>sector_occurrence = cell2mat(arrayfun(@(ii) cellfun(@numel,strfind(FIT_txt,sector{ii})),1:numel(sector),'uni',false')); </code></pre> <p>Now you have a NxM matrix. The element at row i and column j tells how many times <code>sector(j)</code> occurs in <code>FIT_txt(i)</code>.</p> <p>*reading your comments... Aah, but if a sector is found, FIT_txt is exactly equal to the sector, which allows you the simplify all the above this with strcmp and arrayfun:</p> <pre><code>sector_occurrence = cell2mat(arrayfun(@(sectorii) strcmp(FIT_txt,sectorii), sector', 'uni',false)) </code></pre> <p><br><br> Now onto the summation:</p> <p>It's just a vector product of the occurrence vector with <code>FIT_num</code>, and you can get them all in one call by multiplying the <code>sector_occurrence</code> matrix with <code>FIT_num</code>:</p> <pre><code>sumresult = sector_occurrence'*FIT_num; </code></pre> <p>note the transpose operator <code>'</code> because <code>sector_occurrence</code> was defined as <code>NxM</code>.</p> <h2>Example</h2> <pre><code>&gt;&gt; sector=[{'AB10'} ; {'b'}]; &gt;&gt; FIT_txt=[{'AB10'} ; {'a'} ; {'b'} ; {'ZX5b'} ; {'AB10'} ; {'b'}]; &gt;&gt; FIT_num = (1:6)'; &gt;&gt; sector_occurrence = strfind(FIT_txt,sector(ii)) sector_occurrence = 1 0 0 0 0 1 0 0 1 0 0 1 &gt;&gt; sumresult = sector_occurrence'*FIT_num sumresult = 6 9 </code></pre> <p>Of course, it has to be an exact match (which you said it was) <code>b</code> won't be equal to <code>B</code> and also not to <code>bb</code>, only <code>b</code>.</p> <h2>Remark on large data set</h2> <p><code>sector_occurrence</code> is a <code>logical</code> array, so it doesn't need that much memory. But when executing the multiplication with <code>FIT_num</code>, it gets converted to <code>float</code>, which needs 8 times as much space. The end result is a small (in memory) vector, but the intermediary process can melt your pc. You can avoid this by doing the multiplication in a loop:</p> <pre><code>sumresult=NaN(numel(sector),1); %preallocation is a good thing for ii=1:numel(sector) sumresult(ii)=sector_occurrence(:,ii)'*FIT_num; end </code></pre>
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    1. COThanks for that. When I run the first part of the script I am getting following error: "??? Error using ==> cell.strfind at 35 If any of the input arguments are cell arrays, the first must be a cell array of strings and the second must be a character array.".
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    2. COcan you retry? I forgot to add something (see edit). Btw, you actually just need the two last code lines
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    3. COHave tried "sector_occurrence = cell2mat(arrayfun(@(sectorii) strcmp(c,x),sector','uni',false))" - it's not quite working for me. To be honest, I am not understanding the code very well just yet. it doesn't recognise c and x - I have replaces them with FIT_txt and sector (is that correct?), but it's yielding following error: " Error using ==> strcmp Inputs must be the same size or either one can be a scalar.".
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