Re: [Matplotlib-users] Problem with subplot / matplotlib.dates interaction

[Eric F. <ef...@ha...>]

On 2012/08/14 3:15 PM, Damien Irving wrote:
> I've been plotting timeseries data using the matplotlib.dates module and
> have come across an issue when using it in conjunction with the subplot
> command.
>
> For figures with greater than one subplot in a particular column, the
> time (or x) axis ticks and their labels are only printed on the final
> subplot that is plotted, and are missing on all other subplots in that
> column (see example code below). The only exception is when the time
> axis is identical for each plot in the column (you can test this by
> editing my example code at ###) - then all time axis ticks and their
> labels are displayed correctly.
>
> Is this a bug in the subplot source code, or am I missing something?

You are missing something, but it is something that is quite 
non-intuitive and easy to miss: Locators can't be shared among axes. 
The set_major_locator() method assigns its axis to that Locator, 
overwriting any axis that was previously assigned.

The solution is to make a new Locator instance for each axis that needs one.

Eric

>
>
> from pylab import *
> from matplotlib.dates import YEARLY, DateFormatter, rrulewrapper,
> RRuleLocator, drange
> import datetime
>
> # tick every 5th easter #
> rule = rrulewrapper(YEARLY, byeaster=1, interval=5)
> loc = RRuleLocator(rule)
> formatter = DateFormatter('%m/%d/%y')
>
> # data for subplot 1 #
> date1 = datetime.date( 1952, 1, 1 )
> date2 = datetime.date( 2004, 4, 12 )
> delta = datetime.timedelta(days=100)
>
> dates = drange(date1, date2, delta)
> s = rand(len(dates)) # make up some random y values
>
> # plot subplot 1 #
> ax1 = subplot(211)
> plot_date(dates, s)
> ax1.xaxis.set_major_locator(loc)
> ax1.xaxis.set_major_formatter(formatter)
> labels = ax1.get_xticklabels()
> setp(labels, rotation=30, fontsize=10)
>
> # data for subplot 2 #
> date1 = datetime.date( 2052, 1, 1 )  ###( 1952, 1, 1 )
> date2 = datetime.date( 2104, 4, 12 ) ###( 2004, 4, 12 )
>
> dates = drange(date1, date2, delta)
> s = rand(len(dates)) # make up some random y values
>
> # plot subplot 2 #
> ax2 = subplot(212)
> plot_date(dates, s)
> ax2.xaxis.set_major_locator(loc)
> ax2.xaxis.set_major_formatter(formatter)
> labels = ax2.get_xticklabels()
> setp(labels, rotation=30, fontsize=10)
>
> show()
>
>
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