Class: RailsDataExplorer::Chart::ContingencyTable

Inherits:
RailsDataExplorer::Chart show all
Defined in:
lib/rails_data_explorer/chart/contingency_table.rb

Overview

Contingency table and chi squared test are great tools for interpreting A/B tests.

Responsibilities:

* Render a contingency table for bivariate analysis of two categorical
  data series.

Collaborators:

* DataSet

See this project for code to compute chi_square and contingency_coefficient github.com/bioruby/bioruby/blob/master/lib/bio/util/contingency_table.rb

Resources for Chi Squared Test

Instance Attribute Summary

Attributes inherited from RailsDataExplorer::Chart

#output_buffer

Instance Method Summary collapse

Methods inherited from RailsDataExplorer::Chart

#dom_id

Constructor Details

#initialize(_data_set, options = {}) ⇒ ContingencyTable

Returns a new instance of ContingencyTable.



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# File 'lib/rails_data_explorer/chart/contingency_table.rb', line 25

def initialize(_data_set, options = {})
  @data_set = _data_set
  @options = {}.merge(options)
end

Instance Method Details

#compute_chart_attrs ⇒ Object 



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# File 'lib/rails_data_explorer/chart/contingency_table.rb', line 30

def compute_chart_attrs
  x_candidates = @data_set.data_series.find_all { |ds|
    (ds.chart_roles[Chart::ContingencyTable] & [:x, :any]).any?
  }
  y_candidates = @data_set.data_series.find_all { |ds|
    (ds.chart_roles[Chart::ContingencyTable] & [:y, :any]).any?
  }

  x_ds = x_candidates.first
  y_ds = (y_candidates - [x_ds]).first
  return false  if x_ds.nil? || y_ds.nil?

  # Compute @observed_vals, @expected_vals, etc.
  compute_contingency_and_chi_squared!(x_ds, y_ds)

  x_sorted_keys = x_ds.uniq_vals.sort(
    &x_ds.label_sorter(
      nil,
      lambda { |a,b| @observed_vals[b][:_sum] <=> @observed_vals[a][:_sum] }
    )
  )
  y_sorted_keys = y_ds.uniq_vals.sort(
    &y_ds.label_sorter(
      nil,
      lambda { |a,b| @observed_vals[:_sum][b] <=> @observed_vals[:_sum][a] }
    )
  )

  ca = case @data_set.dimensions_count
  when 2
    Utils::RdeTable.new(
      # Top header row
      [
        Utils::RdeTableRow.new(
          :tr,
          [Utils::RdeTableCell.new(:th, '')] +
          x_sorted_keys.map { |x_val| Utils::RdeTableCell.new(:th, x_val) } +
          [Utils::RdeTableCell.new(:th, 'Totals')],
          css_class: 'rde-column_header'
        )
      ] +
      # Data rows
      y_sorted_keys.map { |y_val|
        Utils::RdeTableRow.new(
          :tr,
          [
            Utils::RdeTableCell.new(:th, y_val, css_class: 'rde-row_header')
          ] +
          x_sorted_keys.map { |x_val|
            Utils::RdeTableCell.new(
              :td,
              @observed_vals[x_val][y_val],
              css_class: 'rde-numerical',
              title: [
                "Expected value: #{ number_with_precision(@expected_vals[x_val][y_val], precision: 3, significant: true) }",
                "Percentage of row: #{ number_to_percentage(@delta_attrs[x_val][y_val][:percentage_of_row], precision: 3, significant: true) }",
                "Percentage of col: #{ number_to_percentage(@delta_attrs[x_val][y_val][:percentage_of_col], precision: 3, significant: true) }",
              ].join("\n"),
              style: "color: #{ @delta_attrs[x_val][y_val][:color] };",
            )
          } +
          [
            Utils::RdeTableCell.new(
              :th,
              @observed_vals[:_sum][y_val],
              title: "Percentage of col: #{ number_to_percentage(@delta_attrs[:_sum][y_val][:percentage_of_col], precision: 3, significant: true) }"
            )
          ],
          css_class: 'rde-data_row'
        )
      } +
      # Footer row
      [
        Utils::RdeTableRow.new(
          :tr,
          [Utils::RdeTableCell.new(:th, 'Totals', css_class: 'rde-row_header')] +
          x_sorted_keys.map { |x_val|
            Utils::RdeTableCell.new(
              :th,
              @observed_vals[x_val][:_sum],
              title: "Percentage of row: #{ number_to_percentage(@delta_attrs[x_val][:_sum][:percentage_of_row], precision: 3, significant: true) }"
            )
          } +
          [Utils::RdeTableCell.new(:th, @observed_vals[:_sum][:_sum])],
          css_class: 'rde-column_header'
        )
      ]
    )
  else
    raise(ArgumentError.new("Exactly two data series required for contingency table."))
  end
  ca
end

#render ⇒ Object 



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# File 'lib/rails_data_explorer/chart/contingency_table.rb', line 124

def render
  return ''  unless render?
  ca = compute_chart_attrs
  return ''  unless ca

  content_tag(:div, class: 'rde-chart rde-contingency-table', id: dom_id) do
    content_tag(:h3, "Contingency Table", class: 'rde-chart-title') +
    render_html_table(ca)
  end +
  content_tag(:p, @conclusion)
end

#render? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/rails_data_explorer/chart/contingency_table.rb', line 136

def render?
  # http://en.wikipedia.org/wiki/Pearson's_chi-squared_test#Assumptions
  true
end