Graphing and Plotting

introduction

org-mode supports graphing with gnuplot. This can be done directly with #+plot but it’s very rudimentary. It can also be done with org-babel and I can still feed tables into it.

reading material and citations

ob-gnuplot docs

Has lots of good examples for gnuplot via ob-gnuplot.

org-plot docs

org-plot documentation. Examples feel sparse for my simian mind.

org-plot tutorial

And has the org mode version I can use as reference.

Plotting (with gnuplot) using dates timestamps

Mailing list discussion showing how org-timestamp columns get converted to another format.

gnuplot documentation

plot

ob-gnuplot

ob-gnuplot is the org-babel approach. It’s much more powerful but much more explicit. Basically it allows expression as pure gnuplot code.

reset

The *gnuplot* buffer is basically a repl for gnuplot. In order to ensure settings don’t bleed over between evaluations, use reset to make sure prior runs don’t influence the current run.

reset

separator

Tables fed to gnuplot are tab separated. Set this to properly distinguish columns apart from each other.

set datafile separator "\t"

dates

Dates are harder to work with. There’s a few gnuplot settings that are just a given with dates/times. The dates provided by org-timestamp are converted to the format YYYY-MM-DD-hh:mm:ss. The hours, minutes, and seconds are all always “00”. This is determinable by looking at the *gnuplot* buffer, which will show a temporary path where the file will be emitted such as /var/folders/2g/7v48qrcn2nqgm9_dl173mhd80000gn/T/babel-3445j1/gnuplot-344q9h.

working example

“Real” data!

reset
# org-babel passes gnuplot a payload that's tab separated.
set datafile separator "\t"
set xdata time
set xlabel "time"
set yrange [0:]
# This is the format that org-babel sends to gnuplot.
set timefmt "%Y-%m-%d-%H:%M:%S"
set xrange ["2010-12-03-00:00:00":]
set format x '%Y-%m-%d'
set xtics format "%b %d"
# 564 is the magical width of 80 columns at the present font settings.
set term png size 564, 400
plot data u 1:2 w linespoints title 'ufo sightings', \
     data u 1:3 w linespoints title 'taylor swift songs produced'