[reportlab-users] y-axis scaling issue with GridLinePlot

[Mark Lippett]

Hi folks,

I have just spotted some weird behaviour with GridLinePlot in a django
project.  It seems that the shape of the line plotted is OK, but that the
y-axis labels are out of whack.  The code I am using is below:

class MyLineChartDrawing(Drawing):

  def __init__(self, width=600, height=400, *args, **kw):
    apply(Drawing.__init__,(self,width,height)+args,kw)
    self.add(GridLinePlot(), name='chart')

    self.chart.x = 50 # The x coordinate of the reference point
    self.chart.y = 30 # The y coordinate of the reference point
    self.chart.width = self.width - 150  # The width of the chart
    self.chart.height = self.height - 75 # The height of the chart

    self.chart.data = [[('20110930', 80), ('20111007', 116), ('20111014',
139), ('20111021', 163), ('20111028', 105), ('20111104', 97), ('20111111',
112)]]




  def HttpChart (self, title, XLabel, YLabel, data, isPercent=False):
    return (renderSVG.drawToString(self))


To call this I am simply doing the followingŠ

  d = MyLineChartDrawing(width=chartWidth, height=chartHeight)
  return HttpResponse(d.HttpChart ("", "", "MyYAxisTitle", edata),
'image/svg+xml')



It appears that there is some scaling going on, which becomes quite
dramatic when I add more data.  For example, this self.chart.data list,
which simply adds one tuple to the front of the list, causes scaling to go
from comparatively subtly wrong to about 50% out.

    self.chart.data = [[('20110923', 32), ('20110930', 80), ('20111007',
116), ('20111014', 139), ('20111021', 163), ('20111028', 105),
('20111104', 97), ('20111111', 112)]]

I am using ReportLab 2.5, Django 1.3.0, Python 2.7 running on OSX 10.7.2.


Thanks in advance for any help or advice,

-Mark