This example illustrates how to control scaling of an axis.
By default, ChartDirector will auto-scaled all axes. The
Axis.setAutoScale method controls the top extension, bottom extension and the zero affinity parameters that ChartDirector uses during auto-scaling. The first three charts demonstrates the effects of different top/bottom extensions. (Please refer to
Axis.setAutoScale on what these parameters mean.)
The fourth chart demonstrates that one could exclude a segment on the ends of an axis from scaling using
Axis.setMargin.
The fifth chart demonstrates using manual scaling instead of auto-scaling. A manual linear scale can be configured using
Axis.setLinearScale or
Axis.setLinearScale2. ChartDirector also supports
Axis.setLogScale,
Axis.setLogScale2,
Axis.setDateScale and
Axis.setDateScale2 for configuring manual log and date scales.
[File: pythondemo/axisscale.py] (The CGI version is available as "pythondemo_cgi/axisscale.py".)
#!/usr/bin/python
from pychartdir import *
def createChart(img) :
#The data for the chart
data = [5.5, 3.5, -3.7, 1.7, -1.4, 3.3]
labels = ["Jan", "Feb", "Mar", "Apr", "May", "Jun"]
#Create a XYChart object of size 200 x 180 pixels
c = XYChart(200, 180)
#Set the plot area at (30, 20) and of size 140 x 130 pixels
c.setPlotArea(30, 20, 140, 130)
#Configure the axis as according to the input parameter
if img == "0" :
c.addTitle("No Axis Extension", "arial.ttf", 8)
elif img == "1" :
c.addTitle("Top/Bottom Extensions = 0/0", "arial.ttf", 8)
#Reserve 20% margin at top of plot area when auto-scaling
c.yAxis().setAutoScale(0, 0)
elif img == "2" :
c.addTitle("Top/Bottom Extensions = 0.2/0.2", "arial.ttf", 8)
#Reserve 20% margin at top and bottom of plot area when auto-scaling
c.yAxis().setAutoScale(0.2, 0.2)
elif img == "3" :
c.addTitle("Axis Top Margin = 15", "arial.ttf", 8)
#Reserve 15 pixels at top of plot area
c.yAxis().setMargin(15)
else :
c.addTitle("Manual Scale -5 to 10", "arial.ttf", 8)
#Set the y axis to scale from -5 to 10, with ticks every 5 units
c.yAxis().setLinearScale(-5, 10, 5)
#Set the labels on the x axis
c.xAxis().setLabels(labels)
#Add a color bar layer using the given data. Use a 1 pixel 3D border for the
#bars.
c.addBarLayer3(data).setBorderColor(-1, 1)
#output the chart
c.makeChart("axisscale%s.png" % img)
createChart("0")
createChart("1")
createChart("2")
createChart("3")
createChart("4")
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