using self.method instead of extend self

lib/daru/view/adapters/googlecharts.rb

@@ -235,7 +235,7 @@ def self.add_series(plot, opts={})
         #   from which data has to invoked
         # @return [GoogleVisualr::DataTable] the table object with the data
         #   filled
-        def get_table(data)
+        def self.get_table(data)
           if data.is_a?(Daru::View::Table) &&
              data.table.is_a?(GoogleVisualr::DataTable)
             data.table
@@ -246,7 +246,7 @@ def get_table(data)
           end
         end
 
-        def extract_chart_type(options)
+        def self.extract_chart_type(options)
           # TODO: Imprvoe this method.
           chart_type = options[:type].nil? ? 'Line' : options.delete(:type)
           chart_type = chart_type.to_s.capitalize
@@ -263,7 +263,7 @@ def extract_chart_type(options)
         #
         # TODO : Currently I didn't find use case for multi index.
         # rubocop:disable Metrics/MethodLength
-        def add_data_in_table(data_set)
+        def self.add_data_in_table(data_set)
           case
           when data_set.is_a?(Daru::DataFrame)
             return ArgumentError unless data_set.index.is_a?(Daru::Index)
@@ -286,15 +286,15 @@ def add_data_in_table(data_set)
         end
         # rubocop:enable Metrics/MethodLength
 
-        def add_dataframe_data(data_set)
+        def self.add_dataframe_data(data_set)
           rows = data_set.access_row_tuples_by_indexs(*data_set.index.to_a)
           data_set.vectors.to_a.each do |vec|
             @table.new_column(converted_type_to_js(vec, data_set), vec)
           end
           rows
         end
 
-        def add_array_data(data_set)
+        def self.add_array_data(data_set)
           data_set[0].each_with_index do |col, indx|
             # TODO: below while loop must be improved. Similar thing for
             # above 2 cases.
@@ -310,15 +310,15 @@ def add_array_data(data_set)
           data_set
         end
 
-        def add_vector_data(data_set)
+        def self.add_vector_data(data_set)
           vec_name = data_set.name.nil? ? 'Series' : data_set.name
           @table.new_column(return_js_type(data_set[0]), vec_name)
           rows = []
           data_set.to_a.each { |a| rows << [a] }
           rows
         end
 
-        def converted_type_to_js(vec_name, data_set)
+        def self.converted_type_to_js(vec_name, data_set)
           # Assuming all the data type is same for all the column values.
           case
           when data_set.is_a?(Daru::DataFrame)
@@ -328,14 +328,14 @@ def converted_type_to_js(vec_name, data_set)
           end
         end
 
-        def return_js_type(data)
+        def self.return_js_type(data)
           return if data.nil?
 
           data = data.is_a?(Hash) ? data[:v] : data
           extract_js_type(data)
         end
 
-        def extract_js_type(data)
+        def self.extract_js_type(data)
           case
           when data.is_a?(String)
             'string'

lib/daru/view/adapters/highcharts.rb

@@ -109,7 +109,7 @@ def self.add_series(plot, opts={})
 
         private
 
-        def guess_data(data_set)
+        def self.guess_data(data_set)
           case
           when data_set.is_a?(Daru::DataFrame)
             # TODO : Currently I didn't find use case for multi index.

lib/daru/view/adapters/nyaplot.rb

@@ -37,11 +37,11 @@ def self.init_iruby
 
         private
 
-        def multi_dimension_check(arr)
+        def self.multi_dimension_check(arr)
           arr.all? { |a| a.class==Array }
         end
 
-        def guess_data(data_set)
+        def self.guess_data(data_set)
           case
           when [Daru::DataFrame, Daru::Vector].include?(data_set.class)
             data_set