This patch makes pychart tics behave well with graphs  where very
little variance is in the data but all values are relatively high.
Without it the labels on the y axis get very overcrowded.
 --md@hudora.de

Index: pychart/linear_coord.py
===================================================================
--- pychart/linear_coord.py	(revision 1178)
+++ pychart/linear_coord.py	(working copy)
@@ -31,7 +31,7 @@
             if dmax == dmin:
                 interval = 10
             else:
-                interval = 10 ** (float(int(math.log(dmax-dmin)/math.log(10))))
+                interval = 10 ** (float(int(math.log(dmax)/math.log(10))))
         dmin = min(dmin, pychart_util.round_down(dmin, interval))
         dmax = max(dmax, pychart_util.round_up(dmax, interval) + interval/2.0)
         return dmin, dmax, interval