Hello Néstor,
On 28/08/13, Néstor Espinoza wrote:
> I'm trying to draw confidence bands around some model data-points that I
> have and I think the tutorials that I've read so far that paint areas below
> curves are not what I'm looking for (e.g.,
> http://pyx.sourceforge.net/gallery/graphs/integral.html), because in order
> to paint areas between curves with those methods (i.e., by the method
> suggested in this same mailist here:
> http://osdir.com/ml/python.pyx.users/2008-07/msg00002.html), the trick is
> to paint white below the second curve.
I am not quite sure to understand what you want to do. If it is just
to visualize the confidence of the data, you could use simple error
bars (http://pyx.sourceforge.net/examples/graphstyles/errorbar.html).
I you want it more fancy with a shaded area, the principle is the same
as in the integral example: You take out the paths from the graph, and
those can be manipulated (glued together, split, ...). If this latter
step makes problems, have a look at the joint example.
> Basically in my code I have three vectors, model, model_down and model_up.
> The idea is to plot the confidence bands between the curves model_down and
> model_up (which represent my confidence bads) and plot model as datapoints
> on top: do you have any idea on how to do this?
Best,
Michael
import sys, os
sys.path.insert(0, os.path.expanduser("~/python/PyX-0.12.1"))
import pyx
print pyx.version.version # need 0.12 for canvas layers
from pyx import *
N = 30
xs = [10.0 * i/(N-1) for i in range(N)]
model = [(x-3)*(x-5)*(x-7) for x in xs]
model_upp = [y + 10 for y in model]
model_low = [y - 10 for y in model]
g = graph.graphxy(width=10,
x=graph.axis.linear(title="$x$"),
y=graph.axis.linear(title="$y$"))
g.plot(graph.data.values(x=xs, y=model))
# we need another (identical) graph to avoid plotting lines around the confidence area:
h = graph.graphxy(width=10, x=graph.axis.linkedaxis(g.axes["x"]), y=graph.axis.linkedaxis(g.axes["y"]))
dupp = h.plot(graph.data.values(x=xs, y=model_upp), [graph.style.line()])
dlow = h.plot(graph.data.values(x=xs, y=model_low), [graph.style.line()])
h.doplot()
upp = dupp.path.reversed()
low = dlow.path
x0, y0 = low.atend()
x1, y1 = upp.atbegin()
connect1 = path.line(x0, y0, x1, y1)
area = low << connect1 << upp
area.append(path.closepath())
g.layer("filldata").draw(area, [deco.filled([color.gray(0.8)])])
g.writePDFfile("mini")
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