Module: ColumnsMatcher::Graph

Includes:
GRATR
Defined in:
lib/columns_matcher/graph.rb

Constant Summary collapse

STUB_VALUE = 
1000

Class Method Summary collapse

Class Method Details

.build_dependency_graph(columns) ⇒ Object

column names as the keys and column values as the values Returns a graph of vertices and edges, with weights



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# File 'lib/columns_matcher/graph.rb', line 12

def self.build_dependency_graph(columns)
	combinations_of_column_names = Utilities::get_combinations(columns.keys)

   graph = UndirectedGraph.new

 	combinations_of_column_names.map do |combination_of_column_names|
     first_column_name = combination_of_column_names.first
     second_column_name = combination_of_column_names.last

 		first_column_values = columns[first_column_name]
 		second_column_values = columns[second_column_name]

     if first_column_name == second_column_name
       entropy_of_column = Statistics::entropy(first_column_values)

       graph[first_column_name] = entropy_of_column
     else
       mutual_information_between_columns = Statistics::mutual_information(first_column_values, second_column_values)

       graph.add_edge!(first_column_name, second_column_name, mutual_information_between_columns)
     end
 	end

   graph
end

.get_mappings(pairings, first_graph, second_graph) ⇒ Object

pairings is a 2D array of sub-arrays of size 2 - the results of the Munkres assignment algorithm first_graph and second_graph are UndirectedGraph’s Returns mappings of columns with the keys as columns to match and values as columns to match against



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# File 'lib/columns_matcher/graph.rb', line 57

def self.get_mappings(pairings, first_graph, second_graph)
  first_graph_vertices = first_graph.vertices
  second_graph_vertices = second_graph.vertices

  mappings = Hash.new

  pairings.sort {|first, second| first.first <=> second.first }.each do |pair|
    first_graph_vertex = first_graph_vertices[pair.last]
    second_graph_vertex = second_graph_vertices[pair.first]

    mappings[second_graph_vertex] = first_graph_vertex
  end

  mappings
end

.match_graphs(graph_to_match_against, graph_to_match) ⇒ Object

graph_to_match_against and graph_to_match are are UndirectedGraph’s Returns mappings of columns with the keys as columns to match and values as columns to match against



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# File 'lib/columns_matcher/graph.rb', line 40

def self.match_graphs(graph_to_match_against, graph_to_match)
   graph_to_match_against_vectors = Converter::convert_from_vertices_to_vectors(graph_to_match_against)
   graph_to_match_vectors = Converter::convert_from_vertices_to_vectors(graph_to_match)

   cost_matrix = Converter::convert_from_vectors_to_euclidian_distance_cost_matrix(graph_to_match_vectors, graph_to_match_against_vectors)

   pairings = Statistics::munkres_assignment_algorithm(cost_matrix)

   mappings = Graph::get_mappings(pairings, graph_to_match_against, graph_to_match)

   mappings
end