Revert "Use value_counts instead of tally"

lib/youplot/backends/processing.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module YouPlot
+  # plotting functions.
+  module Backends
+    module Processing
+      module_function
+
+      def count_values(arr, tally: true)
+        # tally was added in Ruby 2.7
+        if tally && 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
+end

lib/youplot/backends/unicode_plot_backend.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require_relative 'processing'
 require 'unicode_plot'
 
 module YouPlot
@@ -15,7 +16,7 @@ module YouPlot
         series = data.series
         # `uplot count`
         if count
-          series = series[0].value_counts.yield_self { |h| [h.keys, h.values] }
+          series = Processing.count_values(series[0])
           params.title = headers[0] if headers
         end
         if series.size == 1