On Sat, Jul 21, 2012 at 10:27 PM, JonBL <jc.bl...@bigpond.net.au> wrote:
>
> I have a line plot where the x-axis values are numbers, with displayed tick
> mark values of 0, 100, 200 ... 500 - a total of 6 tick marks. These values
> represent the number of days since a certain date. I have a function which
> converts a number such as 100, to date string '23-Jun-11', which I want to
> display as the x-axis label instead of 100.
>
> Following the pypib example xaxis_props.py, and printing dir(label) for
> each
> label in the x-axis tick labels, I can see that a label object supports a
> number of methods that might assist in changing the text of tick mark
> labels. I was hoping to use the get_text() method to retrieve the label's
> text (eg, 100), transform this to a date string by my function, and then
> use
> the set_text() method to re-assign the displayed label.
>
> This approach does not work for me. The get_text() method returns a
> zero-length string (not None) for each label, and the set_text() method
> does
> not change the displayed tick mark values. But I can use the set_color()
> method to change the colour of displayed values as per example
> xaxis_props.py.
>
> Any suggestions on how to change the text of displayed x-axis tick marks?
>
> TIA,
> Jon
>
Without example code, it would be difficult to determine what you are doing
incorrectly. That being said, there is an easier solution. If you know
the start date, do the following:
from datetime import datetime, timedelta
startdate = datetime.strptime(datestr, "%d-%m-%y) # you need to look up
the format character for named months.
xdates = np.array([startdate + timedelta(days=i) for i in xrange(501)])
y = np.random.random(xdates.shape)
plt.plot(xdates, y) # This should work, but plot_date() definitely will
work.
Matplotlib recognizes the python datetime object and should format it for
you. You can even control the formatting. See the following examples:
http://matplotlib.sourceforge.net/examples/pylab_examples/date_demo_convert.html?highlight=datetime%20codex
http://matplotlib.sourceforge.net/examples/pylab_examples/date_demo2.html?highlight=datetime%20codex
http://matplotlib.sourceforge.net/examples/api/date_demo.html?highlight=datetime%20codex
http://matplotlib.sourceforge.net/examples/pylab_examples/date_demo1.html?highlight=datetime%20codex
I hope this helps!
Ben Root
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