diff --git a/pygal/graph/bar.py b/pygal/graph/bar.py
index 8c8fa45..2f3cf5c 100644
--- a/pygal/graph/bar.py
+++ b/pygal/graph/bar.py
@@ -63,7 +63,7 @@ class Bar(Graph):
         if rescale and self.secondary_series:
             points = [
                 (x, self._scale_diff + (y - self._scale_min_2nd) * self._scale)
-                for x, y in serie.points]
+                for x, y in serie.points if y is not None]
         else:
             points = serie.points
 
@@ -121,7 +121,7 @@ class Bar(Graph):
                 ymax = new_ymax
 
             left_range = abs(self._box.ymax - self._box.ymin)
-            right_range = abs(ymax - ymin)
+            right_range = abs(ymax - ymin) or 1
             self._scale = left_range / right_range
             self._scale_diff = self._box.ymin
             self._scale_min_2nd = ymin
diff --git a/pygal/graph/datey.py b/pygal/graph/datey.py
index 54a666c..e624284 100644
--- a/pygal/graph/datey.py
+++ b/pygal/graph/datey.py
@@ -50,7 +50,7 @@ class DateY(XY):
 
     def _todate(self, d):
         """ Converts a number to a date """
-        return str(self._offset + datetime.timedelta(seconds=d))
+        return str(self._offset + datetime.timedelta(seconds=d or 0))
 
     def _tonumber(self, d):
         """ Converts a date to a number """
@@ -71,7 +71,7 @@ class DateY(XY):
                             for val in serie.values
                             if val[0] is not None]
                            or [datetime.datetime.fromtimestamp(0)])
-        for serie in self.series:
+        for serie in self.all_series:
             serie.values = [(self._tonumber(v[0]), v[1]) for v in serie.values]
 
         xvals = [val[0]
@@ -89,7 +89,7 @@ class DateY(XY):
         else:
             rng = None
 
-        for serie in self.series:
+        for serie in self.all_series:
             serie.points = serie.values
             if self.interpolate and rng:
                 vals = list(zip(*sorted(
@@ -99,10 +99,10 @@ class DateY(XY):
 
         if self.interpolate and rng:
             xvals = [val[0]
-                     for serie in self.series
+                     for serie in self.all_series
                      for val in serie.interpolated]
             yvals = [val[1]
-                     for serie in self.series
+                     for serie in self.all_series
                      for val in serie.interpolated]
             if xvals:
                 xmin = min(xvals)
diff --git a/pygal/graph/graph.py b/pygal/graph/graph.py
index 04f8db8..f77afd3 100644
--- a/pygal/graph/graph.py
+++ b/pygal/graph/graph.py
@@ -472,7 +472,7 @@ class Graph(BaseGraph):
                 ymax = self._secondary_max
             steps = len(y_pos)
             left_range = abs(y_pos[-1] - y_pos[0])
-            right_range = abs(ymax - ymin)
+            right_range = abs(ymax - ymin) or 1
             scale = right_range / (steps - 1)
             self._y_2nd_labels = [(self._format(ymin + i * scale), pos)
                                   for i, pos in enumerate(y_pos)]
diff --git a/pygal/graph/line.py b/pygal/graph/line.py
index 846be00..e934372 100644
--- a/pygal/graph/line.py
+++ b/pygal/graph/line.py
@@ -60,11 +60,9 @@ class Line(Graph):
     def line(self, serie_node, serie, rescale=False):
         """Draw the line serie"""
         if rescale and self.secondary_series:
-            points = []
-            for x, y in serie.points:
-                if y is not None:
-                    y = self._scale_diff + (y - self._scale_min_2nd) * self._scale
-                points.append((x, y))
+            points = [
+                (x, self._scale_diff + (y - self._scale_min_2nd) * self._scale)
+                for x, y in serie.points if y is not None]
         else:
             points = serie.points
         view_values = list(map(self.view, points))
diff --git a/pygal/graph/verticalpyramid.py b/pygal/graph/verticalpyramid.py
index f4e33fa..308fb76 100644
--- a/pygal/graph/verticalpyramid.py
+++ b/pygal/graph/verticalpyramid.py
@@ -22,7 +22,6 @@ Pyramid chart
 """
 
 from __future__ import division
-from pygal.util import compute_scale, safe_enumerate
 from pygal.adapters import positive
 from pygal.graph.stackedbar import StackedBar
 
@@ -33,7 +32,8 @@ class VerticalPyramid(StackedBar):
     _adapters = [positive]
 
     def _format(self, value):
-        return super(VerticalPyramid, self)._format(abs(value))
+        value = value and abs(value)
+        return super(VerticalPyramid, self)._format(value)
 
     def _get_separated_values(self, secondary=False):
         series = self.secondary_series if secondary else self.series