Amethyst is a small Ruby library/script to extract some essential statistics (mean, median, mode, midpoint and range, quartiles) from series of (numerical) data.

While it can be used as a library from other Ruby programs, its possibly most interesting use is as a command line filter: it can read the data series to be analyzed from its standard input (one datum per line), and it produces the relevant statistics on its standard output. Typical usage would be something like:

$ produce_some_data | amethyst

For example, statistics on the number of lines of the source files for one of my ongoing creative works at the time of writing:

$ wc -l oppure/ganka/ganka[0-9]* | head -n -1 | amethyst
# count: 43
# min: 48
# max: 274
# mid: 161
# range: 226

# mean: 102.3953488372093
# stddev: 42.266122304343874

# mode(s): 48 51 59 75 79 86 93 102 104

# median: 97
# quartiles: 79 97 110
# IQR: 31

When acting as a filter, Amethyst will check if its standard output has been redirected/piped to another program, in which case, by default, it will also produce commands that can be fed to gnuplot to produce a visual representation of the distribution of the dataset, including a histogram and a box plot:

$ produce_some_data | amethyst | gnuplot -p

Command line options such as --[no-]histogram and --[no-]boxplot can be used to override the default choices on what to plot (if anything), and options such as --dumb can be used to let gnuplot output a textual approximation of the plot(s) on the terminal itself.