C M, on 2011-01-27 02:03, wrote: > > 3) I am getting just hammered with the following error *a lot* in date > > plotting lately: > > > > ValueError: ordinal must be >= 1 > > > OK, I made up a small runnable sample to show this with bar(). (Using > code that someone else wrote[1]). This code runs when using > plot_date(), but if you comment that out and comment in the ax.bar() > line, it will give this ValueError. > > > import matplotlib.pyplot as plt > import matplotlib as mpl > import numpy as np > import datetime as dt > > # Make a series of events 1 day apart > x = mpl.dates.drange(dt.datetime(2009,10,1), > dt.datetime(2010,1,15), > dt.timedelta(days=1)) > # Vary the datetimes so that they occur at random times > # Remember, 1.0 is equivalent to 1 day in this case... > x += np.random.random(x.size) > > # We can extract the time by using a modulo 1, and adding an arbitrary base > date > times = x % 1 + int(x[0]) # (The int is so the y-axis starts at midnight...) > > # I'm just plotting points here, but you could just as easily use a bar. > fig = plt.figure() > ax = fig.add_subplot(111) > > #comment out: > ax.plot_date(x, times, 'ro') >
Hi C. M., The reason you were getting that error is because unless you specify otherwise, ax.bar will make the bottom of the bars at 0 - which isn't an allowed date, hence the error. Change your bar line to this (I also added align='center', but you can remove it if you want): > #comment in bot = times.min().round() ax.bar(x, times-bot, bottom=bot, align='center') > > ax.yaxis_date() > fig.autofmt_xdate() > > plt.show() best, -- Paul Ivanov 314 address only used for lists, off-list direct email at: http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7
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