Add zero in config

pygal/config.py

@@ -73,6 +73,7 @@ class Config(object):
     interpolate = None
     # Number of interpolated points between two values
     interpolation_precision = 250
+    zero = 0
 
     def __init__(self, **kwargs):
         """Can be instanciated with config kwargs"""

pygal/graph/bar.py

@@ -84,8 +84,8 @@ class Bar(Graph):
         return stack_vals
 
     def _compute(self):
-        self._box.ymin = min(min(self._values), 0)
+        self._box.ymin = min(min(self._values), self.zero)
-        self._box.ymax = max(max(self._values), 0)
+        self._box.ymax = max(max(self._values), self.zero)
         x_step = len(self.series[0].values)
         x_pos = [x / float(x_step) for x in range(x_step + 1)
         ] if x_step > 1 else [0, 1]  # Center if only one value

pygal/graph/line.py

@@ -37,7 +37,7 @@ class Line(Graph):
                     for val in serie.points]
 
     def _fill(self, values):
-        zero = self.view.y(min(max(0, self._box.ymin), self._box.ymax))
+        zero = self.view.y(min(max(self.zero, self._box.ymin), self._box.ymax))
         return ([(values[0][0], zero)] +
                 values +
                 [(values[-1][0], zero)])