YouPlot/lib/uplot/preprocessing.rb

require 'csv'

module Uplot
  module Preprocessing
    module_function

    def input(input, delimiter, headers, transpose)
      arr = read_csv(input, delimiter)
      headers = get_headers(arr, headers, transpose)
      series = get_series(arr, headers, transpose)
      Data.new(headers, series)
    end

    def read_csv(input, delimiter)
      CSV.parse(input, col_sep: delimiter)
         .delete_if do |i|
           i == [] or i.all? nil
         end
    end

    # Transpose different sized ruby arrays
    # https://stackoverflow.com/q/26016632
    def transpose2(arr)
      Array.new(arr.map(&:length).max) { |i| arr.map { |e| e[i] } }
    end

    def get_headers(arr, headers, transpose)
      if headers
        if transpose
          arr.map(&:first)
        else
          arr[0]
        end
      end
    end

    def get_series(arr, headers, transpose)
      if transpose
        if headers
          arr.map { |row| row[1..-1] }
        else
          arr
        end
      else
        if headers
          transpose2(arr[1..-1])
        else
          transpose2(arr)
        end
      end
    end

    def count(arr)
      # tally was added in Ruby 2.7
      if Enumerable.method_defined? :tally
        arr.tally
      else
        # https://github.com/marcandre/backports
        arr.each_with_object(Hash.new(0)) { |item, res| res[item] += 1 }
           .tap { |h| h.default = nil }
      end
        .sort { |a, b| a[1] <=> b[1] }
        .reverse
        .transpose
    end
  end
end