Simson Garfinkel wrote:
> Hi. It's me again, asking about dates again.
>
> is there any easy way to a collection using dates on the X axes?
> I've taken the collection example from the website and adopted it so
> that there is a use_dates flag. Set it to False and spirals demo
> appears. Set it to True and I get this error:
Yes, it looks like a bug in the handling of units in the Collection base
class; unit conversion is done at drawing time, but needs either to be
done earlier, or to be done independently in the get_datalim method.
Maybe one of the units-support experts will pick this up and fix it. I
can't do more now.
Eric
>
> Traceback (most recent call last):
> File "mpl_collection2.py", line 51, in <module>
> ax.add_collection(col, autolim=True)
> File "/Library/Frameworks/Python.framework/Versions/2.6/lib/
> python2.6/site-packages/matplotlib/axes.py", line 1312, in
> add_collection
> self.update_datalim(collection.get_datalim(self.transData))
> File "/Library/Frameworks/Python.framework/Versions/2.6/lib/
> python2.6/site-packages/matplotlib/collections.py", line 144, in
> get_datalim
> offsets = transOffset.transform_non_affine(offsets)
> File "/Library/Frameworks/Python.framework/Versions/2.6/lib/
> python2.6/site-packages/matplotlib/transforms.py", line 1914, in
> transform_non_affine
> self._a.transform(points))
> File "/Library/Frameworks/Python.framework/Versions/2.6/lib/
> python2.6/site-packages/matplotlib/transforms.py", line 1408, in
> transform
> return affine_transform(points, mtx)
> ValueError: Invalid vertices array.
>
>
> The code is below.
>
> Thanks!
>
> =========================
> import matplotlib
> import matplotlib.pyplot
> from matplotlib import collections, transforms
> from matplotlib.colors import colorConverter
> import numpy as N
>
> import datetime
>
> use_dates = False
>
> nverts = 50
> npts = 100
>
> # Make some spirals
> r = N.array(range(nverts))
> theta = N.array(range(nverts)) * (2*N.pi)/(nverts-1)
> xx = r * N.sin(theta)
> yy = r * N.cos(theta)
> spiral = zip(xx,yy)
>
> # Make some offsets
> rs = N.random.RandomState([12345678])
>
> if not use_dates:
> xo = [i for i in range(0,100)]
> else:
> xo = [datetime.date(1990,1,1)+datetime.timedelta(10)*i for i in
> range(0,100)] # new version
>
> yo = rs.randn(npts)
> xyo = zip(xo, yo)
> colors = [colorConverter.to_rgba(c) for c in
> ('r','g','b','c','y','m','k')]
>
> fig = matplotlib.pyplot.figure()
> ax = fig.add_subplot(1,1,1)
>
> if use_dates:
> import matplotlib.dates as mdates
> years = mdates.YearLocator() # every year
> months = mdates.MonthLocator() # every month
> yearsFmt = mdates.DateFormatter('%Y')
> ax.xaxis.set_major_locator(years)
> ax.xaxis.set_major_formatter(yearsFmt)
> ax.set_xlim(datetime.date(1990,1,1),datetime.date(1992,12,31))
>
> col = collections.LineCollection([spiral], offsets=xyo,
> transOffset=ax.transData)
> trans = fig.dpi_scale_trans + transforms.Affine2D().scale(1.0/72.0)
> col.set_transform(trans) # the points to pixels transform
> ax.add_collection(col, autolim=True)
> col.set_color(colors)
>
> ax.autoscale_view()
> ax.set_title('LineCollection using offsets')
> matplotlib.pyplot.show()
>
>
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