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PO
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15947987
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2013-04-11T11:47:19.570
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2013-04-11T11:54:49.547
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2017-05-23T12:27:11.860
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15947617
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2
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Here's a way to compute it manually, assuming the set of n vectors is stored in a matrix <code>A</code>, row by row: <ol> <li>Obtain all possible pairs of indices (see <a href="https://stackoverflow.com/questions/7446946/how-to-generate-all-pairs-from-two-vectors-in-matlab-using-vectorised-code">this question</a> for possible answers). For instance: <pre><code>[idx2, idx1] = find(ones(N, N)); </code></pre> The corresponding pairs are given by: <pre><code>pairs = [idx1(:), idx2(:)]; </code></pre> Alternatively, if you're not interested in repetitions (e.g. you don't want the sum A1+A1, etc.), you can use <code>nchoosek</code>: <pre><code>pairs = nchoosek(1:N, 2) idx1 = pairs(:, 1); idx2 = pairs(:, 2); </code></pre></li> <li>Use each pair of indices to sum the corresponding rows in <code>A</code>: <pre><code>sums = A(idx1(:), :) + A(idx2(:), :); </code></pre> Alternatively, if you want the total sum of elements for each pair of Ai and Aj, you can do <code>sum(A(idx1(:), :) + A(idx2(:), :), 2)</code> instead.</li> </ol> <h3>Example</h3> Here's an example for <code>N = 3</code>: <pre><code>A = [1 2 3; 2 3 4; 3 4 5]; N = size(A, 1); [idx2, idx1] = find(ones(N, N)); pairs = [idx1(:), idx2(:)]; sums = A(idx1(:), :) + A(idx2(:), :); </code></pre> The result is: <pre><code>pairs = 1 1 1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3 sums = 2 4 6 3 5 7 4 6 8 3 5 7 4 6 8 5 7 9 4 6 8 5 7 9 6 8 10 </code></pre>
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singulars
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1. This table or related slice is empty.
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1. POsum of k combination of vectors from n vectors
 singulars
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