title: Matplotlib/Pandas: Zoom Part of a Plot with Time Series
body: <p>my task is simple: I have a time series <code>ts</code> (Euro Swiss Franc daily exchange rates between 2010 and 2014) to plot. In that plot I would like to highlight a certain time interval by zooming into it. However, the zoomed window stays simply empty (see code below). Furthermore, I have a problem by selecting the x-range of the zoomed-in window since I do not know how to properly transform the dates to the internal integer representation of the matplotlib. </p>
  
  <p>Thanks in advance for your help! </p>
  
  <p>Here is my code: </p>
  
  <pre><code>import numpy as np
  import pandas as pd
  from matplotlib import pyplot as plt
  from mpl_toolkits.axes_grid1.inset_locator import zoomed_inset_axes 
  from mpl_toolkits.axes_grid1.inset_locator import mark_inset
  
  # Load the time series
  ts = pd.read_csv('./Data/EUR_CHF_Exchange_Rates/EUR_CHF_daily.csv',sep=';', parse_dates=['time'], index_col = 'time',decimal=',')
  ts = ts['EUR/CHF']
  ts = ts.sort_index(ascending=True)
  
  # Plot
  fig = plt.figure(figsize=(14,5))
  ax = plt.axes()
  ts.plot() # ts is my time series
  
  # Label the axis
  ax.set_xlabel('')
  ax.set_ylabel('EUR/CHF')
  
  #I want to select the x-range for the zoomed region. I have figured it out suitable values
  # by trial and error. How can I pass more elegantly the dates as something like
  # x1 = '2012-05-09'
  # x2 = '2012-09-02'
  x1 = 15439.0
  x2 = 15588.0
  
  # select y-range for zoomed region
  y1 = 1.15
  y2 = 1.25
  
  # Make the zoom-in plot:
  axins = zoomed_inset_axes(ax, 2, loc=1) # zoom = 2
  axins.plot(ts)
  axins.set_xlim(x1, x2)
  axins.set_ylim(y1, y2)
  plt.xticks(visible=False)
  plt.yticks(visible=False)
  mark_inset(ax, axins, loc1=2, loc2=4, fc="none", ec="0.5")
  plt.draw()
  plt.savefig('daily_exchange_rates.pdf') # The zoomed window is empty!!!! 
  </code></pre>