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POEigen: m(:, v > 0) and m(:, [1,3])
 

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  1. POEigen: m(:, v > 0) and m(:, [1,3])
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    <p>I'm trying to implement Matlab's m(:, v > 0) and m(:,[1,3]) in Eigen. So far I got the following functions:</p> <pre><code>MatrixXd select_cols(const MatrixXd src, const Matrix&lt;bool, 1, Dynamic&gt; cond) { MatrixXd dst(src.rows(), cond.count()); unsigned int i = 0; for (unsigned int j = 0; j &lt; cond.cols(); j++) { if (cond(0,j)) { dst.col(i++) = src.col(j); } } return dst; } MatrixXd select_cols(const MatrixXd src, const Matrix&lt;unsigned int, 1, Dynamic&gt; idx) { MatrixXd dst(src.rows(), idx.size()); for (unsigned int i = 0; i &lt; idx.size(); ++i) { dst.col(i) = src.col(idx[i]); } return dst; } </code></pre> <p>However, I thought that the following snippet will work, but it does't:</p> <pre><code>Eigen::MatrixXd m1(3,3); Eigen::Matrix&lt;unsigned int, 1, Eigen::Dynamic&gt; v(3); m1 &lt;&lt; 1,2,3, 4,5,6, 7,8,9; v &lt;&lt; 2,0,2; Eigen::MatrixXd m2 = Eigen::select_cols(m1, v.array() &gt; 1); </code></pre> <p>There is the error: </p> <pre><code>utest.cpp:88:62: error: call of overloaded ‘select_cols(Eigen::MatrixXd&amp;, const Eigen::CwiseUnaryOp&lt;std::binder2nd&lt;std::greater&lt;unsigned int&gt; &gt;, const Eigen::ArrayWrapper&lt;Eigen::Matrix&lt;unsigned int, 1, -0x00000000000000001&gt; &gt; &gt;)’ is ambiguous utest.cpp:88:62: note: candidates are: common.h:29:14: note: Eigen::MatrixXd Eigen::select_cols(Eigen::MatrixXd, Eigen::Matrix&lt;unsigned int, 1, -0x00000000000000001&gt;) common.h:32:14: note: Eigen::MatrixXd Eigen::select_cols(Eigen::MatrixXd, Eigen::Matrix&lt;bool, 1, -0x00000000000000001&gt;) </code></pre>
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    1. USliborw
    1. USliborw
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    1. VO
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      1. POEigen: m(:, v > 0) and m(:, [1,3])
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    2. VO
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      1. POEigen: m(:, v > 0) and m(:, [1,3])
      1. USTry Hard
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    1. CO`m(:, m > 0)` doesn't really make sense in Matlab. `m > 0` will have the same dimensions as `m`. So if `m` is a 2D matrix, then you are trying to choose the columns with a logical 2D matrix which shouldn't work. So what behavior are you expecting from it?
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      1. POEigen: m(:, v > 0) and m(:, [1,3])
      1. USDan
    2. COI suppose you may either be looking for `m(m>0)`, `m(:,any(m>0))`, `m(:,all(m>0))` or `m(:,sum(m>0))`
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      1. POEigen: m(:, v > 0) and m(:, [1,3])
      1. USDennis Jaheruddin
    3. COI have updated the question
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      1. POEigen: m(:, v > 0) and m(:, [1,3])
      1. USliborw
 

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