title: Overlap between two datasets
body: <p>I am currently working on two sets of data that provide monthly prices for the same financial products between 02/2013 and 09/2018. The two datasets do not have every monthly price for every product, and Dataset 1 has more accurate data than Dataset 2. </p>
  
  <p>I would like to find a way to merge the two datasets to obtain a resulting dataset that has the most accurate data (from Dataset1), and complete this data with available data from Dataset 2. </p>
  
  <p>In addition, I would like to know what pourcentage of the data overlaps between the two datasets. </p>
  
  <p>Let's say these are samples of my two datasets : </p>
  
  <pre><code>Dataset 1
   201602     201603     201604                 
  1 103.5     102.4      101.6 
  2 0         0          104.2              
  3 101.6     101.7      102     
  
  Dataset 2
   201602     201603     201604                 
  1 0         103.1      102.8 
  2 102.3     103.5      104.5              
  3 0         101.5      102.3
  </code></pre>
  
  <p>I would like to obtain :</p>
  
  <pre><code>Dataset 1
  `201602`   `201603`   `201604`                 
  1 103.5     102.4      101.6 
  2 102.3     103.5      104.2              
  3 101.6     101.7      102 
  </code></pre>
  
  <p>And an indication that my overlap = 5/9 = 55.6%</p>
  
  <p>I have more than 1000 financial products, so I'm looking for the simplest possible code. </p>
  
  <p>Thank you in advance for you help !</p>