Class Gruff::Line
In: lib/gruff/line.rb
Parent: Gruff::Base

Here‘s how to make a Line graph:

  g = Gruff::Line.new
  g.title = "A Line Graph"
  g.data 'Fries', [20, 23, 19, 8]
  g.data 'Hamburgers', [50, 19, 99, 29]
  g.write("test/output/line.png")

There are also other options described below, such as baseline_value, baseline_color, hide_dots, and hide_lines.

Methods

Attributes

baseline_color  [RW]  Color of the baseline
baseline_value  [RW]  Draw a dashed line at the given value
dot_radius  [RW] 
hide_dots  [RW]  Hide parts of the graph to fit more datapoints, or for a different appearance.
hide_lines  [RW]  Hide parts of the graph to fit more datapoints, or for a different appearance.
line_width  [RW]  Dimensions of lines and dots; calculated based on dataset size if left unspecified

Public Class methods

Call with target pixel width of graph (800, 400, 300), and/or ‘false’ to omit lines (points only).

 g = Gruff::Line.new(400) # 400px wide with lines

 g = Gruff::Line.new(400, false) # 400px wide, no lines (for backwards compatibility)

 g = Gruff::Line.new(false) # Defaults to 800px wide, no lines (for backwards compatibility)

The preferred way is to call hide_dots or hide_lines instead.

[Source]

# File lib/gruff/line.rb, line 39
  def initialize(*args)
    raise ArgumentError, "Wrong number of arguments" if args.length > 2
    if args.empty? or ((not Numeric === args.first) && (not String === args.first)) then
      super()
    else
      super args.shift
    end

    @hide_dots = @hide_lines = false
    @baseline_color = 'red'
    @baseline_value = nil
  end

Public Instance methods

[Source]

# File lib/gruff/line.rb, line 118
  def contains_one_point_only?(data_row)
    # Spin through data to determine if there is just one_value present.
    one_point = false
    data_row[DATA_VALUES_INDEX].each do |data_point|
      if !data_point.nil?
        if one_point
          # more than one point, bail
          return false
        else
          # there is at least one data point
          return true
        end
      end
    end
    return one_point
  end

[Source]

# File lib/gruff/line.rb, line 52
  def draw
    super

    return unless @has_data

    # Check to see if more than one datapoint was given. NaN can result otherwise.
    @x_increment = (@column_count > 1) ? (@graph_width / (@column_count - 1).to_f) : @graph_width

    if (defined?(@norm_baseline)) then
      level = @graph_top + (@graph_height - @norm_baseline * @graph_height)
      @d = @d.push
      @d.stroke_color @baseline_color
      @d.fill_opacity 0.0
      @d.stroke_dasharray(10, 20)
      @d.stroke_width 5
      @d.line(@graph_left, level, @graph_left + @graph_width, level)
      @d = @d.pop
    end

    @norm_data.each do |data_row|
      prev_x = prev_y = nil

      @one_point = contains_one_point_only?(data_row)

      data_row[DATA_VALUES_INDEX].each_with_index do |data_point, index|
        new_x = @graph_left + (@x_increment * index)
        next if data_point.nil?

        draw_label(new_x, index)

        new_y = @graph_top + (@graph_height - data_point * @graph_height)

        # Reset each time to avoid thin-line errors
        @d = @d.stroke data_row[DATA_COLOR_INDEX]
        @d = @d.fill data_row[DATA_COLOR_INDEX]
        @d = @d.stroke_opacity 1.0
        @d = @d.stroke_width line_width ||
          clip_value_if_greater_than(@columns / (@norm_data.first[DATA_VALUES_INDEX].size * 4), 5.0)


        circle_radius = dot_radius ||
          clip_value_if_greater_than(@columns / (@norm_data.first[DATA_VALUES_INDEX].size * 2.5), 5.0)

        if !@hide_lines and !prev_x.nil? and !prev_y.nil? then
          @d = @d.line(prev_x, prev_y, new_x, new_y)
        elsif @one_point
          # Show a circle if there's just one_point
          @d = @d.circle(new_x, new_y, new_x - circle_radius, new_y)
        end
        @d = @d.circle(new_x, new_y, new_x - circle_radius, new_y) unless @hide_dots

        prev_x = new_x
        prev_y = new_y
      end

    end

    @d.draw(@base_image)
  end

[Source]

# File lib/gruff/line.rb, line 112
  def normalize
    @maximum_value = [@maximum_value.to_f, @baseline_value.to_f].max
    super
    @norm_baseline = (@baseline_value.to_f / @maximum_value.to_f) if @baseline_value
  end

[Validate]