require 'gnuplotrb'
require 'daru'
include GnuplotRB

dv = Daru::Vector.new [:a, :a, :a, :b, :b], type: :category

Plot.new [dv.frequencies, with: 'histogram'], xrange: -1..2, yrange: 0..10

Plot.new [dv.frequencies(:percentage), with: 'histogram'], xrange: -1..2, yrange: 0..100

df = Daru::DataFrame.new({
  x: [1, 2, 3, 4, 5, 6, 7, 8],
  y: [3, 2, 3, 5, 6, 1, 2, 3],
  cat: ['III', 'II', 'I', 'I', 'II', 'I', 'III', 'III']
})
df[:cat] = df[:cat].to_category categories: ['I', 'II', 'III']
df[:cat].type

dfs = df.split_by_category :cat
# The line below is because of this issue: https://github.com/SciRuby/gnuplotrb/issues/8
dfs.each { |df| df.index = df.nrows.times.to_a }
###
Plot.new(
  *dfs.map { |df| [df, using: 'x:y'] }, xrange: 0..10, yrange: 0..10
)