Add gnuplot script for plotting pressure curves

logs/README.md

@@ -15,3 +15,11 @@ Pumpdown curve: elapsed (seconds, float) and mbar.
 To acquire: `python3 acquire.py` and give it a tag/comment to stdin. Then press the pumpdown button or turn the scope on.
 
 Elapsed is 0 at the moment the script detected a pumpdown event.
+
+## Plotting with `gnuplot`
+You can use the `plot-pressure.gnuplot` script to plot the pressure graphs.  Use it like this:
+
+```terminal
+$ gnuplot
+gnuplot> load "plot-pressure.gnuplot"
+```

logs/plot-pressure.gnuplot

@@ -0,0 +1,6 @@
+FILES = system("ls -1 pressure-*.csv")
+LABEL = system("ls -1 pressure-*.csv | sed 's/pressure-\\(.*\\)\\..*/\\1/'")
+
+set logscale y
+
+plot for [i=1:words(FILES)] word(FILES,i) using 1:2 title word(LABEL,i) with lines