Class: RailsDataExplorer::Chart::BoxPlotGroup

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

Overview

Responsibilities:

* Render a group of box plots for bivariate analysis of a categorical and
  a numerical data series. One box plot is rendered for each distinct
  categorical value.

Collaborators:

* DataSet

Resources:

Instance Attribute Summary

Attributes inherited from RailsDataExplorer::Chart

#output_buffer

Instance Method Summary collapse

Methods inherited from RailsDataExplorer::Chart

#dom_id, #render?

Constructor Details

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

Returns a new instance of BoxPlotGroup.



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

def compute_chart_attrs
  x_candidates = @data_set.data_series.find_all { |ds|
    (ds.chart_roles[Chart::BoxPlotGroup] & [:x, :any]).any?
  }
  y_candidates = @data_set.data_series.find_all { |ds|
    (ds.chart_roles[Chart::BoxPlotGroup] & [:y, :any]).any?
  }
  x_ds = x_candidates.first
  y_ds = (y_candidates - [x_ds]).first
  return false  if x_ds.nil? || y_ds.nil?

  # initialize values_hash
  values_hash = y_ds.uniq_vals.inject({}) { |m,y_val|
    m[y_val] = []
    m
  }
  # populate values hash
  y_ds.values.each_with_index { |y_val, idx|
    next  if (y_val.nil? || Float::NAN == y_val)
    values_hash[y_val] << x_ds.values[idx]
  }
  y_sorted_keys = y_ds.uniq_vals.sort(
    &y_ds.label_sorter(
      nil,
      lambda { |a,b| a <=> b }
    )
  )
  sorted_values = y_sorted_keys.map { |y_val| values_hash[y_val] }

  # Compute min and max values based on interquartile range of each
  # boxplot. Objective is to normalize boxplots so that the widest chart
  # uses almost the entire space available.
  # Iterate over all individual boxplots
  global_min = Float::INFINITY
  global_max = -Float::INFINITY
  sorted_values.each { |x_vals|
    ds = DataSeries.new('_', x_vals)
    desc_stats = ds.descriptive_statistics
    # compute first and third quartile. Use min and max if they are nil
    # for very small data series with only one or two entries.
    q1 = desc_stats.detect { |e| '25%ile' == e[:label] }[:value] || x_vals.min
    q3 = desc_stats.detect { |e| '75%ile' == e[:label] }[:value] || x_vals.max
    iqr = (q3 - q1) * 1.5
    local_min = [x_vals.min, q1 - iqr].max
    global_min = [global_min, local_min].min
    local_max = [x_vals.max, q3 + iqr].min
    global_max = [global_max, local_max].max
  }

  {
    values: sorted_values,
    category_labels: y_sorted_keys,
    min: global_min,
    max: global_max,
    base_width: 100,
    base_height: 960,
    axis_tick_format: x_ds.axis_tick_format,
    num_box_plots: y_ds.uniq_vals_count,
    axis_scale: DataSeries.new('_', [global_min, global_max]).axis_scale(:d3)
  }
end

#render ⇒ Object 



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# File 'lib/rails_data_explorer/chart/box_plot_group.rb', line 92

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

  svg_trs = ca[:category_labels].map { |cat_label|
    %(
      <tr>
        <td style="vertical-align: middle;">#{ cat_label }</td>
        <td style="vertical-align: middle; width: 100%">
          <svg class="box" style="height: #{ ca[:base_width] }px; width: 100%;"></svg>
        </td>
      </tr>
    )
  }.join.html_safe
  %(
    <div id="#{ dom_id }" class="rde-chart rde-box-plot-group">
      <table>#{ svg_trs }</table>

      <script type="text/javascript">
        (function() {
          var base_width = #{ ca[:base_width] },
              base_height = #{ ca[:base_height] },
              margin = { top: 10, right: 40, bottom: 10, left: 40 },
              width = base_width - margin.left - margin.right,
              height = base_height - margin.top - margin.bottom;

          var min = #{ ca[:min] },
              max = #{ ca[:max] };

          var chart = d3.box()
                        .whiskers(iqr(1.5))
                        .width(width)
                        .height(height)
                        .tickFormat(#{ ca[:axis_tick_format] });

          var data = #{ ca[:values].to_json };

          chart.domain([min, max]);
          chart.scale(#{ ca[:axis_scale] });

          var svg = d3.select("##{ dom_id }").selectAll("svg")
                      .data(data)
                    .append("g")
                      .attr("transform", "rotate(90) translate(" + margin.left + " -" + (height + margin.bottom) + ")")
                      .call(chart);

          // Function to compute the interquartile range.
          function iqr(k) {
            return function(d, i) {
              var q1 = d.quartiles[0],
                  q3 = d.quartiles[2],
                  iqr = (q3 - q1) * k,
                  i = -1,
                  j = d.length;
              while (d[++i] < q1 - iqr);
              while (d[--j] > q3 + iqr);
              return [i, j];
            };
          }
        })();
      </script>
    </div>
  )
end