plot_date with multiple subplots

Community matplotlib-users
1

I have a short script to plot 20 years of river flow data. I can use
the plot_date command to create a plot, using this snippet:
f = figure()
ax1 = f.add_subplot(111)
ax1.plot_date(dates0,y1,'g', label='observed', xdate=True,visible=True)
ax1.plot_date(dates1,y2,'r', label='simulated', xdate=True,visible=True)
years = YearLocator(1, month=6, day=30) # every year
months = MonthLocator(1) # every month
ax1.set_xlim(date2num(datetime.date(1990,1,1)),date2num(datetime.date(1999,12,31)))
ax1.xaxis.set_major_locator(years)
ax1.xaxis.set_minor_locator(months)
labels = ax1.get_xticklabels()
setp(labels, fontsize=8,visible=True)

The problem is with the x-axis (time axis) labels when I add a second
subplot, to add the next time segment. I change the above to ax1 =
f.add_subplot(211), and then:
ax2 = f.add_subplot(212)
ax2.plot_date(dates0,y1,'g') #plots the time series
ax2.plot_date(dates1,y2,'r') #need to call twice, unlike plot,
plot_date takes one set
ax2.set_xlim(date2num(datetime.date(2000,1,1)),date2num(datetime.date(2009,12,31)))
ax2.xaxis.set_major_locator(years)
ax2.xaxis.set_minor_locator(months)
setp(labels, fontsize=8,visible=True)

The x-axis labels only appear for the last subplot. I'm guessing that
plot_date assumes that more than one subplot must share a time axis.
There must be a simple way to stop plot_date from doing this, if this
is indeed the problem. Any guidance would be appreciated.

Thanks,
Ed

2

I have a short script to plot 20 years of river flow data. I can use
the plot_date command to create a plot, using this snippet:
f = figure()
ax1 = f.add_subplot(111)
ax1.plot_date(dates0,y1,'g', label='observed', xdate=True,visible=True)
ax1.plot_date(dates1,y2,'r', label='simulated', xdate=True,visible=True)
years = YearLocator(1, month=6, day=30) # every year
months = MonthLocator(1) # every month
ax1.set_xlim(date2num(datetime.date(1990,1,1)),date2num(datetime.date(1999,12,31)))
ax1.xaxis.set_major_locator(years)
ax1.xaxis.set_minor_locator(months)
labels = ax1.get_xticklabels()
setp(labels, fontsize=8,visible=True)

The problem is with the x-axis (time axis) labels when I add a second
subplot, to add the next time segment. I change the above to ax1 =
f.add_subplot(211), and then:
ax2 = f.add_subplot(212)
ax2.plot_date(dates0,y1,'g') #plots the time series
ax2.plot_date(dates1,y2,'r') #need to call twice, unlike plot,
plot_date takes one set
ax2.set_xlim(date2num(datetime.date(2000,1,1)),date2num(datetime.date(2009,12,31)))
ax2.xaxis.set_major_locator(years)
ax2.xaxis.set_minor_locator(months)
setp(labels, fontsize=8,visible=True)

The x-axis labels only appear for the last subplot. I'm guessing that
plot_date assumes that more than one subplot must share a time axis.
There must be a simple way to stop plot_date from doing this, if this
is indeed the problem. Any guidance would be appreciated.

Thanks,
Ed

3

i use something like that:

from datetime import datetime, timedelta
import matplotlib.pyplot as pl
import matplotlib.ticker as ticker
import matplotlib.dates as mdates

dates1 = [datetime(2005,5,11)+n*timedelta(days=1) for n in range(500)]
dates2 = [datetime(...

ax1 = pl.subplot(2,1,1)
ax1.plot(dates1, y1, 'r')
ax1.fmt_xdata = mdates.DateFormatter('%Y-%m-%d')

ax2 = pl.subplot(2,1,2)
ax2.plot(dates2, ...

that's what you want?

regards, yoshi