title: How to combine two csv documents to a figure with dirffrent timespan?
body: <p>compare temperatures in two places with different timespan</p>
  
  <p>temperature data in death_valley is from 2014.7.1-2014.12.29
  while
  data in sitka is from 2014.1.1-2014.12.29</p>
  
  <pre><code>dates=[]
  for row in reader_death_valley:
      current_date=datetime.strptime(row[0],'%Y-%m-%d')
      dates.append(current_date)    
  </code></pre>
  
  <p>and I don't know how to set date as x_axis</p>
  
  <pre><code>plt.plot(dates,highs_death_valley,c='red')
  plt.plot(dates,highs_sitka,c='blue')
  </code></pre>
  
  <p>ValueError: x and y must have same first dimension, but have shapes (313,) and (0,)</p>