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diff --git a/lib/knapsack_solver/graph_printer.rb b/lib/knapsack_solver/graph_printer.rb
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+require 'gnuplot'
+
+module KnapsackSolver
+  # This class provides support for making graphs from statistics of datasets
+  # solving results. It uses Gnuplot and also generates a Gnuplot config file
+  # for each generated graph.
+  class GraphPrinter
+    # Initializes printer for graph data (graphs, Gnuplot config files).
+    #
+    # @param dataset_filenames [Array<String>] dataset filenames
+    # @param stats [Hash] statistics of results
+    # @param out_dir [String] statistics of results to print
+    def initialize(dataset_filenames, stats, out_dir)
+      @dataset_basenames = file_basenames(dataset_filenames)
+      @stats = stats
+      @out_dir = out_dir
+    end
+
+    # Create graphs from statistics and Gnuplot configuration files.
+    def print
+      stats_to_datasets.each do |title, ds|
+        ofn = File.join(@out_dir, title + '.png')
+        plot(title, ds, ofn)
+      end
+    end
+
+    protected
+
+    # Create graph.
+    #
+    # @param title [String] title of the graph
+    # @param data [Array<Gnuplot::DataSet>] Gnuplot datasets to plot
+    # @param filename [String] path to the output image file
+    def plot(title, data, filename)
+      Gnuplot.open do |gp|
+        Gnuplot::Plot.new(gp, &plot_config(title, 'dataset', 'y', data, filename))
+      end
+      File.open(File.join(File.dirname(filename), File.basename(filename, '.png') + '.gnuplot'), 'w') do |gp|
+        Gnuplot::Plot.new(gp, &plot_config(title, 'dataset', 'y', data, filename))
+      end
+    end
+
+    # Creates Gnuplot datasets from statistics.
+    #
+    # @return [Array<Gnuplot::DataSet>] Gnuplot datasets created from the statistics.
+    def stats_to_datasets
+      graphs = @stats.values.first.values.first.first.keys
+      x_data = @stats.keys
+      datasets(graphs, x_data)
+    end
+
+    # Creates Gnuplot datasets from statistics.
+    #
+    # @param graphs [Array] array of graph titles
+    # @param x_data [Array] array of X axis values
+    def datasets(graphs, x_data)
+      graphs.each_with_object({}) do |g, gnuplot_datasets|
+        @stats.each_value do |s|
+          gnuplot_datasets[g.to_s] = s.each_key.with_object([]) do |method, o|
+            o << plot_dataset(method.to_s, x_data, @stats.map { |_, v| v[method].first[g] })
+          end
+        end
+      end
+    end
+
+    # Create dataset from provided title, X axis data and Y axis data.
+    #
+    # @param title [String] Gnuplot dataset title
+    # @param x_data [Array] Array of X values
+    # @param y_data [Array] Array of Y values
+    # @return [Gnuplot::DataSet] Gnuplot dataset.
+    def plot_dataset(title, x_data, y_data)
+      Gnuplot::DataSet.new([x_data, y_data]) { |ds| ds.title = escape_gnuplot_special_chars(title) }
+    end
+
+    # Creates Gnuplot plot configuration (configuration text lines).
+    #
+    # @param title [String] graph title
+    # @param xlabel [String] label of X axis
+    # @param ylabel [String] label of Y axis
+    # @param plot_datasets [Array<Gnuplot::DataSet>] Gnuplot datasets for plotting
+    # @param out_file [String] output file
+    # @return [lambda] Lambda for setting plot configuration.
+    def plot_config(title, xlabel, ylabel, plot_datasets, out_file)
+      lambda do |plot|
+        plot.term('png')
+        plot.output(out_file)
+        plot.title("'#{escape_gnuplot_special_chars(title)}'")
+        plot.ylabel("'#{escape_gnuplot_special_chars(ylabel)}'")
+        plot.xlabel("'#{escape_gnuplot_special_chars(xlabel)}'")
+        plot.key('outside')
+        plot.data = plot_datasets
+      end
+    end
+
+    # Escapes Gnuplot special characters.
+    #
+    # @param str [String] a string
+    # @return [Strnig] the string with Gnuplot special chars escaped
+    def escape_gnuplot_special_chars(str)
+      # underscore means subscript in Gnuplot
+      str.gsub('_', '\_')
+    end
+
+    # Gets basenames of supplied file paths.
+    #
+    # @param paths [Array<String>] path to files
+    # @return [Array<String>] basenames of the paths
+    def file_basenames(paths)
+      paths.each_with_object([]) do |path, basenames|
+        basenames << File.basename(path, File.extname(path))
+      end
+    end
+  end
+end