How to plot ratios of values with Gnuplot

Gnuplot is a tool that can generate script-driven graphics, including plots of functions and data samples. Gnuplot contains a useful scripting language that allows you to process raw data files while producing graphics. For example, you can plot ratios of different values contained in raw data files.

If you would like to plot the ratio of data belonging to two different columns in a data file:

$ cat my.txt
1     10    20
2     20    25
. . .
gnuplot> plot "my.txt" using 1:($3/$2) title "ratio of the 3rd col over the 2nd col" with lp 

If you would like to plot the ratio of data belonging to two different data files:

$ cat A.txt
1 10
2 20
. . .
$ cat B.txt
1 11
2 30
. . .
gnuplot> plot "< join A.txt B.txt" using 1:($3/$2) "ratio of data in B.txt over data in A.txt" lp 

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