Fix dot with log scale. Fix #201

CHANGELOG

@@ -10,6 +10,8 @@ V 2.0.0 UNRELEASED
 	Add new Box plot modes and outliers and set extremes as default (#226 #121 #149) (thanks djezar)
 	Add secondary_range option to set range for secondary values. (#203)
 	Maps are now plugins, they are removed from pygal core and moved to packages (pygal_maps_world, pygal_maps_fr, pygal_maps_ch, ...) (#225)
+	Dot now supports negative values
+	Fix dot with log scale (#201)
 
 V 1.7.0
 	Remove DateY and replace it by real XY datetime, date, time and timedelta support. (#188)

demo/moulinrouge/tests.py

@@ -186,12 +186,12 @@ def get_test_routes(app):
 
     @app.route('/test/dot')
     def test_dot():
-        dot = Dot()
+        dot = Dot(logarithmic=True)
         dot.x_labels = map(str, range(4))
         dot.add('a', [1, lnk(3, 'Foo'), 5, 3])
-        dot.add('b', [2, 2, 0, 2, .1])
-        dot.add('c', [5, 1, 5, lnk(3, 'Bar')])
-        dot.add('d', [5, 5, lnk(0, 'Babar'), 3])
+        dot.add('b', [2, -2, 0, 2, .1])
+        dot.add('c', [5, 1, 50, lnk(3, 'Bar')])
+        dot.add('d', [-5, 5, lnk(0, 'Babar'), 3])
 
         return dot.render_response()
 

pygal/css/graph.css

@@ -107,6 +107,10 @@
   stroke-width: 5px;
 }
 
+{{ id }}.dot.negative {
+  fill: transparent;
+}
+
 {{ id }}.series text {
   stroke: none;
 }

pygal/graph/dot.py

@@ -22,32 +22,47 @@ Dot chart
 """
 
 from __future__ import division
-from pygal.util import decorate, cut, safe_enumerate
-from pygal.adapters import positive
+from pygal.util import decorate, cut, safe_enumerate, cached_property
 from pygal.graph.graph import Graph
+from pygal.view import View, ReverseView
+from math import log10
 
 
 class Dot(Graph):
     """Dot graph"""
 
-    _adapters = [positive]
-
     def dot(self, serie, r_max):
         """Draw a dot line"""
         serie_node = self.svg.serie(serie)
         view_values = list(map(self.view, serie.points))
         for i, value in safe_enumerate(serie.values):
             x, y = view_values[i]
-            size = r_max * value
-            value = self._format(value)
+
+            if self.logarithmic:
+                log10min = log10(self._min) - 1
+                log10max = log10(self._max or 1)
+
+                if value != 0:
+                    size = r_max * (
+                        (log10(abs(value)) - log10min) /
+                        (log10max - log10min)
+                    )
+                else:
+                    size = 0
+            else:
+                size = r_max * (abs(value) / (self._max or 1))
+
             metadata = serie.metadata.get(i)
             dots = decorate(
                 self.svg,
                 self.svg.node(serie_node['plot'], class_="dots"),
                 metadata)
-            self.svg.node(dots, 'circle', cx=x, cy=y, r=size,
-                          class_='dot reactive tooltip-trigger')
+            self.svg.node(dots, 'circle',
+                          cx=x, cy=y, r=size,
+                          class_='dot reactive tooltip-trigger' + (
+                              ' negative' if value < 0 else ''))
 
+            value = self._format(value)
             self._tooltip_data(dots, value, x, y, classes='centered')
             self._static_value(serie_node, value, x, y)
 
@@ -69,10 +84,30 @@ class Dot(Graph):
         self._y_labels = list(zip(
             self.y_labels or cut(self.series, 'title'), y_pos))
 
+    def _set_view(self):
+        """Assign a view to current graph"""
+        view_class = ReverseView if self.inverse_y_axis else View
+
+        self.view = view_class(
+            self.width - self.margin_box.x,
+            self.height - self.margin_box.y,
+            self._box)
+
+    @cached_property
+    def _values(self):
+        """Getter for series values (flattened)"""
+        return [abs(val) for val in super()._values if val != 0]
+
+    @cached_property
+    def _max(self):
+        """Getter for the maximum series value"""
+        return (self.range[1] if (self.range and self.range[1] is not None)
+                else (max(map(abs, self._values)) if self._values else None))
+
     def _plot(self):
         r_max = min(
             self.view.x(1) - self.view.x(0),
             (self.view.y(0) or 0) - self.view.y(1)) / (
-                2 * (self._max or 1) * 1.05)
+                2 * 1.05)
         for serie in self.series:
             self.dot(serie, r_max)

pygal/view.py

@@ -314,8 +314,8 @@ class LogView(View):
         if y is None or y <= 0 or self.log10_ymax - self.log10_ymin == 0:
             return 0
         return (self.height - self.height *
-                (log10(y) - self.log10_ymin)
-                / (self.log10_ymax - self.log10_ymin))
+                (log10(y) - self.log10_ymin) / (
+                    self.log10_ymax - self.log10_ymin))
 
 
 class XLogView(View):