Please post a standalone example that reproduces your problem.
I tried your example with some junk data but no such exception is raised.
However, there has been a report of a similar ordinal value problem
which I think is not fixed yet, but that problem only occurs when two
and more axes are shared.
See if below helps,
* move the axhline call after the plotting commands.
* autoscale only after all the necessary plot elements are in place.
Again, please post a standalone example that reproduces your problem.
Regards,
-JJ
On Tue, Jul 14, 2009 at 9:50 AM, M Osborne<osbo...@gmail.com> wrote:
> I am trying to plot some historical trend data, where x is a date and
> y is a percentage.
>
> When I try to insert a horizontal line with ax1.axhline(y=80,
> linewidth=1, color='r'), matplotlib breaks, with an error "
> ValueError: ordinal must be >= 1".
>
> The Traceback most recent call is, File
> "/usr/lib64/python2.4/site-packages/matplotlib/dates.py", line 170, in
> _from_ordinalf
> dt = datetime.datetime.fromordinal(ix)"
>
> Without the axhline element, matplotlib handles the data fine, and
> plots nice weekly dates.
>
> I'm guessing based on the error that axhline is manually forcing
> autoscale off and/or matplotlib can no longer interpret the date
> values for x?
>
> Below is the matplotlib snippet of my code:
>
> fig = plt.figure(figsize=(20,10))
> font = { 'fontname':'Tahoma', 'fontsize':12 }
> ax1 = fig.add_subplot(211)
> ax1.set_ylim(0,100)
> ax1.autoscale_view(tight=False, scalex=True, scaley=False)
> ax1.grid(True)
> ax1.axhline(y=80, linewidth=1, color='r')
> ax1.set_ylim(0,100)
> ax1.autoscale_view(tight=False, scalex=True, scaley=False)
> ax1.plot(timestamp, percentu, 'ko-' )
> ax1.plot(timestamp, percentl, 'b--', linewidth=2)
> ax2 = fig.add_subplot(212)
> ax2.grid(True)
> ax2.plot(predict_x, predict_y, 'bs--', linewidth=2)
> plt.savefig("plot.pdf")
>
>
> Thank you in advance!
>
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