Added tests for box, fixed regressions

pygal/graph/box.py

@@ -23,6 +23,7 @@ Box plot
 from __future__ import division
 from pygal.graph.graph import Graph
 from pygal.util import compute_scale, decorate
+from math import floor
 
 
 class Box(Graph):
@@ -123,23 +124,44 @@ class Box(Graph):
     @staticmethod
     def _box_points(values):
         """
-        Return a 5-tuple of Q1 - 1.5 * IQR, Q1, Median, Q3, and Q3 + 1.5 * IQR for a list of numeric values
+        Return a 5-tuple of Q1 - 1.5 * IQR, Q1, Median, Q3, and Q3 + 1.5 * IQR for a list of numeric values.
+
+        The iterator values may include None values.
 
         Uses quartile definition from  Mendenhall, W. and Sincich, T. L. Statistics for Engineering and the
         Sciences, 4th ed. Prentice-Hall, 1995.
         """
-        n = len(values)
+        def median(seq):
+            n = len(seq)
+            if n % 2 == 0:  # seq has an even length
+                return (seq[n // 2] + s[n // 2 - 1]) / 2
+            else:  # seq has an odd length
+                return seq[n // 2]
+
+        # sort the copy in case the originals must stay in original order
+        s = sorted([x for x in values if x is not None])
+        n = len(s)
         if not n:
             return 0, 0, 0, 0, 0
         else:
-            s = sorted(values)  # sort the copy in case the originals must stay in original order
-            if n % 2 == 0:  # n is even
-                q2 = (values[n // 2] + values[n // 2 + 1]) / 2
-            else:
-                q2 = values[(n + 1) // 2]
+            q2 = median(s)
+            # See 'Method 3' in http://en.wikipedia.org/wiki/Quartile
+            if n % 2 == 0:  # even
+                q1 = median(s[:n // 2])
+                q3 = median(s[n // 2:])
+            else:  # odd
+                if n == 1:  # special case
+                    q1 = s[0]
+                    q3 = s[0]
+                elif n % 4 == 1:  # n is of form 4n + 1 where n >= 1
+                    m = (n - 1) // 4
+                    q1 = 0.25 * s[m-1] + 0.75 * s[m]
+                    q3 = 0.75 * s[3*m] + 0.25 * s[3*m + 1]
+                else:  # n is of form 4n + 3 where n >= 1
+                    m = (n - 3) // 4
+                    q1 = 0.75 * s[m] + 0.25 * s[m+1]
+                    q3 = 0.25 * s[3*m+1] + 0.75 * s[3*m+2]
 
-            q1 = values[int(round((n + 1) / 4))]
-            q3 = values[int(round((3 * n + 3) / 4))]
             iqr = q3 - q1
             q0 = q1 - 1.5 * iqr
             q4 = q3 + 1.5 * iqr

pygal/test/test_box.py

@@ -0,0 +1,62 @@
+# -*- coding: utf-8 -*-
+# This file is part of pygal
+#
+# A python svg graph plotting library
+# Copyright © 2012-2013 Kozea
+#
+# This library is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option) any
+# later version.
+#
+# This library is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with pygal. If not, see <http://www.gnu.org/licenses/>.
+from pygal.graph.box import Box
+from pygal import Box as ghostedBox
+
+
+def test_quartiles():
+    a = [-2.0, 3.0, 4.0, 5.0, 8.0]  # odd test data
+    q0, q1, q2, q3, q4 = Box._box_points(a)
+
+    assert q1 == 7.0 / 4.0
+    assert q2 == 4.0
+    assert q3 == 23 / 4.0
+    assert q0 == 7.0 / 4.0 - 6.0  # q1 - 1.5 * iqr
+    assert q4 == 23 / 4.0 + 6.0  # q3 + 1.5 * iqr
+
+    b = [1.0, 4.0, 6.0, 8.0]  # even test data
+    q0, q1, q2, q3, q4 = Box._box_points(b)
+
+    assert q2 == 5.0
+
+    c = [2.0, None, 4.0, 6.0, None]  # odd with None elements
+    q0, q1, q2, q3, q4 = Box._box_points(c)
+
+    assert q2 == 4.0
+
+    d = [4]
+    q0, q1, q2, q3, q4 = Box._box_points(d)
+
+    assert q0 == 4
+    assert q1 == 4
+    assert q2 == 4
+    assert q3 == 4
+    assert q4 == 4
+
+
+def test_simple_box():
+    box = ghostedBox()
+    box.add('test1', [-1, 2, 3, 3.1, 3.2, 4, 5])
+    box.add('test2', [2, 3, 5, 6, 6, 4])
+    box.title = 'Box test'
+    q = box.render_pyquery()
+
+    assert len(q(".axis.y")) == 1
+    assert len(q(".legend")) == 2
+    assert len(q(".plot .series rect")) == 2

pygal/test/test_config.py

@@ -18,7 +18,7 @@
 # along with pygal. If not, see <http://www.gnu.org/licenses/>.
 from pygal import (
     Line, Dot, Pie, Radar, Config, Bar, Funnel, Worldmap,
-    SupranationalWorldmap, Histogram, Gauge)
+    SupranationalWorldmap, Histogram, Gauge, Box)
 from pygal._compat import u
 from pygal.test.utils import texts
 from pygal.test import pytest_generate_tests, make_data
@@ -270,7 +270,7 @@ def test_no_data():
 def test_include_x_axis(Chart):
     chart = Chart()
     if Chart in (Pie, Radar, Funnel, Dot, Gauge, Worldmap,
-                 SupranationalWorldmap, Histogram):
+                 SupranationalWorldmap, Histogram, Box):
         return
     if not chart.cls._dual:
         data = 100, 200, 150

pygal/test/test_graph.py

@@ -68,7 +68,9 @@ def test_render_to_png(Chart, datas):
 def test_metadata(Chart):
     chart = Chart()
     v = range(7)
-    if Chart == pygal.XY:
+    if Chart in (pygal.Box,):
+        return  # summary charts cannot display per-value metadata
+    elif Chart == pygal.XY:
         v = list(map(lambda x: (x, x + 1), v))
     elif Chart == pygal.Worldmap or Chart == pygal.SupranationalWorldmap:
         v = list(map(lambda x: x, i18n.COUNTRIES))