Editing Tips and tricks
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==Tiny helper functions== | ==Tiny helper functions== | ||
This is a list of tiny helper functions (the equivalent of e.g., shell aliases), the kind one would have on its {{Path|.octaverc}} file. | This is a list of tiny helper functions (the equivalent of e.g., shell aliases), the kind one would have on its {{Path|.octaverc}} file. | ||
=== 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 less 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 | <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> | ||
</table> | </table> | ||
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==General== | ==General== | ||
===A funny formatting trick with fprintf found by chance=== | |||
Imagine that you want to create a text table with fprintf with 2 columns of 15 characters width and both right justified. How to do this thing? | |||
That's easy: | |||
If the variable Text is a cell array of strings (of length <15) with two columns and a certain number of rows, simply type for the kth row of Text | |||
fprintf('%15.15s | %15.15s\n', Text{k,1}, Text{k,2}); | |||
The syntax '%<n>.<m>s' allocates '<n>' places to write chars and display the '<m>' first characters of the string to display. | |||
Example: | |||
octave:1> Text={'Hello','World'}; | |||
octave:2> fprintf('%15.15s | %15.15s\n', Text{1,1}, Text{1,2}) | |||
Hello | World | |||
===Load Comma Separated Values (*.csv) files=== | |||
A=textread("file.csv", "%d", "delimiter", ","); | |||
B=textread("file.csv", "%s", "delimiter", ","); | |||
inds = isnan(A); | |||
B(!inds) = num2cell(A(!inds)) | |||
This gets you a 1 column cell array. You can reshape it to the original size by using the <code>reshape</code> function | |||
The next version of octave (3.6) implements the <code>CollectOutput</code> switch as seen in example 8 here: http://www.mathworks.com/help/techdoc/ref/textscan.html | |||
===Using Variable Strings in Octave Commands=== | |||
For example, to plot data using a string variable as a legend: | |||
Option 1 (simplest): | |||
legend = "-1;My data;"; | |||
plot(x, y, legend); | |||
Option 2 (to insert variables): | |||
plot(x, y, sprintf("-1;%s;", dataName)); | |||
Option 3 (not as neat): | |||
legend = 'my legend'; | |||
plot_command = ['plot(x,y,\';',legend,';\')']; | |||
eval(plot_command); | |||
These same tricks are useful for reading and writing data files with unique names, etc. | |||
===Vectorizing Tricks=== | ===Vectorizing Tricks=== | ||
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====Other references==== | ====Other references==== | ||
*MATLAB array manipulation tips and tricks by Peter Acklam: | *MATLAB array manipulation tips and tricks by Peter Acklam: 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 | ||