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87 lines
2.9 KiB
Org Mode
87 lines
2.9 KiB
Org Mode
* Guide
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This is an overview of the capabilities of =feedgnuplot= and a set of example
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recipes. The [[https://github.com/dkogan/feedgnuplot/][documentation]] provides a complete reference. The capabilities of
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gnuplot itself are demonstrated at [[http://www.gnuplot.info/demo/][its demo page]].
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First, a trivial plot: let's plot a sinusoid
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE 'say sin($_/5.)' | \
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feedgnuplot
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#+END_SRC
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#+RESULTS:
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[[file:guide-1.svg]]
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This was a trivial plot, and was trivially-easy to make: we gave the tool one
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column of data with no specific instructions, and we got a plot.
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Here each point we plotted was 2-dimensional (has an x value an a y value), but
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we passed in only one number for each point. This is what is expected without
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=--domain=, so =feedgnuplot= filled in sequential integers (0, 1, 2, ...) for
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the x coordinate. Without =--domain= and without =--dataid=, each line of input
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is interpreted as =y0 y1 y2...=. So we can plot a sin and a cos together:
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE '$th = $_/100.*2.*3.14159; $s=sin($th); $c=cos($th); say "$c $s"' | \
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feedgnuplot
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#+END_SRC
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#+RESULTS:
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[[file:guide-2.svg]]
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Note that, the lines may have different numbers of points. To plot the cos from
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every line, but a sin from every 5th line:
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE '$th = $_/100.*2.*3.14159; $s=sin($th); $c=cos($th);
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if($.%5) { say "$c"; } else { say "$c $s"; }' | \
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feedgnuplot
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#+END_SRC
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#+RESULTS:
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[[file:guide-3.svg]]
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If we pass in two columns and =--domain=, =feedgnuplot= will use one for the x,
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and the other for the y. With =--domain= and without =--dataid=, each line of
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input is interpreted as =x y0 y1 y2...=. Let's plot =sin(theta)= vs.
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=cos(theta)=, i.e. a circle:
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE '$th = $_/100.*2.*3.14159; $s=sin($th); $c=cos($th); say "$c $s"' | \
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feedgnuplot --domain
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#+END_SRC
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#+RESULTS:
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[[file:guide-4.svg]]
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Hmmm. We asked for a circle, but this looks more like an ellipse. Why? Because
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gnuplot is autoscaling the x and y axes independently to fill the plot window.
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We can scale the axes /together/ by passing =--square=, and we get a circle:
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE '$th = $_/100.*2.*3.14159; $s=sin($th); $c=cos($th); say "$c $s"' | \
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feedgnuplot --domain --square
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#+END_SRC
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#+RESULTS:
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[[file:guide-5.svg]]
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Again, we can have multiple =y= in each line, and each line may have a different
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number of =y=. Let's plot a circle /and/ an ellipse, sampled more coarsely:
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#+BEGIN_SRC sh :results file link :exports both
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seq 100 | \
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perl -nE '$th = $_/100.*2.*3.14159; $s=sin($th); $c=cos($th);
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if($.%5) { say "$c $s"; } else { $s2 = $s/2; say "$c $s $s2"; }' | \
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feedgnuplot --domain --square
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#+END_SRC
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#+RESULTS:
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[[file:guide-6.svg]]
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