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Tips and tricks: Difference between revisions
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=== replace help with man === | === replace help with man === | ||
If you use octave too much, you'll find yourself trying to use {{Codeline|help}} instead of {{Codeline|man}} on bash. This function will fix that so you can use {{Codeline|man}} in your octave instance (you can also do the opposite, create a {{Codeline|help}} alias in bash but {{Codeline|man}} has | If you use octave too much, you'll find yourself trying to use {{Codeline|help}} instead of {{Codeline|man}} on bash. This function will fix that so you can use {{Codeline|man}} in your octave instance (you can also do the opposite, create a {{Codeline|help}} alias in bash but {{Codeline|man}} has fewer characters). | ||
{{Code|alias to help|<pre> | {{Code|alias to help|<pre> | ||
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<tr><td>element multiplication</td><td><code>A.*B</code></td><td><code>product(A,B) </code></td></tr> | <tr><td>element multiplication</td><td><code>A.*B</code></td><td><code>product(A,B) </code></td></tr> | ||
<tr><td>element division</td><td><code>A./B</code></td><td><code>quotient(A,B) </code></td></tr> | <tr><td>element division</td><td><code>A./B</code></td><td><code>quotient(A,B) </code></td></tr> | ||
<tr><td>transpose*</td><td><code>A'</code></td><td><code>A.transpose()</code></td></tr> | <tr><td>transpose*</td><td><code>A.'</code></td><td><code>A.transpose()</code></td></tr> | ||
<tr><td>select element m,n of A**</td><td><code>A(m,n)</code></td><td><code>A(m-1,n-1)</code></td></tr> | <tr><td>select element m,n of A**</td><td><code>A(m,n)</code></td><td><code>A(m-1,n-1)</code></td></tr> | ||
<tr><td>select row N of A**</td><td><code>A(N,:)</code></td><td><code>A.row(N-1)</code></td></tr> | <tr><td>select row N of A**</td><td><code>A(N,:)</code></td><td><code>A.row(N-1)</code></td></tr> | ||
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<tr><td>number of rows</td><td><code>size(A,1)</code></td><td><code>A.rows()</code></td></tr> | <tr><td>number of rows</td><td><code>size(A,1)</code></td><td><code>A.rows()</code></td></tr> | ||
<tr><td>number of columns</td><td><code>size(A,2)</code></td><td><code>A.cols()</code></td></tr> | <tr><td>number of columns</td><td><code>size(A,2)</code></td><td><code>A.cols()</code></td></tr> | ||
<tr><td>range</td><td><code>0.1:0.2:0.9</code></td><td><code>Range (0.1, 0.9, 0.2).matrix_value ()</code></td></tr> | |||
</table> | </table> | ||
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====Other references==== | ====Other references==== | ||
*MATLAB array manipulation tips and tricks by Peter Acklam: http://home.online.no/~pjacklam/matlab/doc/mtt/index.html | *MATLAB array manipulation tips and tricks by Peter Acklam: https://web.archive.org/web/20151030212438/http://home.online.no/~pjacklam/matlab/doc/mtt/index.html | ||
*The MathWorks: Code Vectorization Guide: http://www.mathworks.com/support/tech-notes/1100/1109.html | *The MathWorks: Code Vectorization Guide: http://www.mathworks.com/support/tech-notes/1100/1109.html | ||
[[Category:Tips and tricks]] | [[Category:Tips and tricks]] | ||
===Changing BLAS=== | ===Changing BLAS=== | ||
Many Octave functions are wrappers to optimized numerical libraries, notably BLAS and ATLAS. It is possible to achieve impressive performance gains by simply using a library tuned to your platform. One example is using OpenBLAS to replace the default BLAS implementation ([https://web.archive.org/web/20140217072457/http://www.stat.cmu.edu/~nmv/2013/07/09/for-faster-r-use-openblas-instead-better-than-atlas-trivial-to-switch-to-on-ubuntu/ further details]). | |||
On some Linux distributions, this just takes a few commands. For instance, on Ubuntu, it usually suffices to run | |||
On Linux, this just takes a few commands | |||
sudo apt-get install libopenblas-base libatlas3gf-base | sudo apt-get install libopenblas-base libatlas3gf-base | ||
followed by | |||
sudo update-alternatives --config libblas.so.3 | sudo update-alternatives --config libblas.so.3 | ||
and | and then selecting the openblas option. | ||