Here's a simple example of what I mean: Depending on whether you use 100 or 101 points, "y(x)=1/x" is plotted with or without a spurious almost vertical line at 0.
The reason is that with 101 points, one evaluation throws a ZeroDivision exception which graph.data.function catches and turns into "y=None", which tells graph.style.line to cut the line. With 100 points, "singular" values" merely reach 50, which is way beyond my clipping range but not that far on the way to infinity, of course. In my third example, I demonstrate what I mean by range cutting using a wrapper. This again avoids the extra vertical line. I think the graph.data.function() family (or the line style?) could really use an absmax argument, or ymin and ymax, which would turn on a rangecutter. Having this on by default would be useful, but the example also shows that a good default value would be difficult to choose - it could be based on the min and max for the yaxis (times 10 or so), although that could cause other problems. Michael P.S.: I'm not sure about this list's policy reagrding attachments. Sorry if the pdf should be out of place.
#!/usr/bin/python3
from pyx import *
def rangecutter(x, bound=20):
if (abs(x) < bound):
return x
return None
unit.set(wscale=10)
g = graph.graphxy(width=10, ratio=1,
x=graph.axis.linear(min=-2, max=2),
y=graph.axis.linear(min=-2, max=2))
g.plot(graph.data.function("y(x)=1/x", points=100), [graph.style.line([color.rgb.red, style.linewidth.THick])])
g.plot(graph.data.function("y(x)=1/x", points=101), [graph.style.line([color.rgb.green, style.linewidth.Thick])])
g.plot(graph.data.functionxy(lambda x: rangecutter(1/x), points=100), [graph.style.line([color.rgb.blue])])
g.writePDFfile()
singular.pdf
Description: video/flv
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