Implement Y ticks (#33)

Author: 284km

lib/rubyplot/artist/axes.rb

@@ -23,10 +23,14 @@ class Axes < Base
       attr_reader :y_axis
       # Array of X ticks.
       attr_reader :x_ticks
+      # Array of Y ticks.
+      attr_reader :y_ticks
       # Array denoting co-ordinates in pixels of the origin of X and Y axes.
       attr_reader :origin
       # Number of X ticks.
       attr_accessor :num_x_ticks
+      # Number of Y ticks.
+      attr_accessor :num_y_ticks
       # Position of the legend box.
       attr_accessor :legend_box_position
       # Set true if title is to be hidden.
@@ -78,7 +82,9 @@ def initialize(figure)
         @x_axis = Rubyplot::Artist::XAxis.new(self)
         @y_axis = Rubyplot::Artist::YAxis.new(self)
         @x_ticks = nil
+        @y_ticks = nil
         @num_x_ticks = 5
+        @num_y_ticks = 4
         @legend_box_position = :top
       end
 
@@ -107,6 +113,7 @@ def draw
         configure_title
         configure_legends
         assign_x_ticks
+        assign_y_ticks
         actually_draw
       end
 
@@ -179,6 +186,10 @@ def x_ticks= x_ticks
         @x_ticks = x_ticks
       end
 
+      def y_ticks= y_ticks
+        @y_ticks = y_ticks
+      end
+
       def x_title= x_title
         @x_axis.title = x_title
       end
@@ -221,6 +232,26 @@ def assign_x_ticks
         end
       end
 
+      def assign_y_ticks
+        unless @y_ticks
+          val_distance = (@y_range[1] - @y_range[0]).abs / @num_y_ticks.to_f
+          @y_ticks = (@y_range[0]..@y_range[1]).step(val_distance).map { |i| i }
+        end
+        unless @y_ticks.all? { |t| t.is_a?(Rubyplot::Artist::YTick) }
+          inter_ticks_distance = @y_axis.length / (@num_y_ticks - 1)
+          @y_ticks.map!.with_index do |tick_label, i|
+            Rubyplot::Artist::YTick.new(
+              self,
+              abs_x: @origin[0],
+              abs_y: @y_axis.abs_y1 - (i * inter_ticks_distance),
+              label: Rubyplot::Utils.format_label(tick_label),
+              length: 6,
+              label_distance: 50
+            )
+          end
+        end
+      end
+
       def add_plot plot_type, *args, &block
         plot = with_backend plot_type, *args
         yield(plot) if block_given?
@@ -271,6 +302,7 @@ def normalize_plotting_data
       def actually_draw
         @x_axis.draw
         @x_ticks.each(&:draw)
+        @y_ticks.each(&:draw)
         @y_axis.draw
         @texts.each(&:draw)
         @legend_box.draw

lib/rubyplot/artist/tick/y_tick.rb

@@ -1,6 +1,24 @@
 module Rubyplot
   module Artist
     class YTick < Tick::Base
+      def initialize(*)
+        super
+        @label = Rubyplot::Artist::Text.new(
+          @label_text.to_s,
+          @owner,
+          abs_x: @abs_x - 5 - @label_distance,
+          abs_y: @abs_y + @length,
+          pointsize: @owner.marker_font_size,
+        )
+      end
+
+      def draw
+        @backend.draw_line(
+          x1: @abs_x, y1: @abs_y, x2: @abs_x - @length, y2: @abs_y,
+          stroke_opacity: @tick_opacity,
+          stroke_width: @tick_width)
+        @label.draw
+      end
     end
     # class YTick
   end

spec/axes_spec.rb

@@ -32,6 +32,7 @@
         axes.y_title = "Y title"
         axes.x_ticks = ['Jan', 'Feb', 'March', 'April', 'May', 'June',  'July',
                         'August', 'September', 'October', 'November', 'December']
+        axes.y_ticks = ['5', '10', '15', '20', '25', '30']
       end
 
       it "plots stacked bar in a small size" do