title: How can I join pandas dataframes on multiple columns with a tolerance?
body: <p>Say I have two pandas dataframes, both containing x and y coordinates (floats). I want to join the dataframes on the two columns, i.e. where <code>df1['x']==df2['x'] &amp;&amp; df1['y']==df2['y']</code> <strong>within some tolerance</strong> to get a result like so:</p>
  
  <pre><code>df1=  x  ,  y  ,  tag1 
       1.2   1.3    'ab'
  
  df2=  x  ,  y  ,  tag2 
       1.1   1.2    'cd'
  </code></pre>
  
  <p>becomes</p>
  
  <pre><code>df_result=  x  ,  y  ,  tag1 , tag2
             1.2   1.3    'ab'   'cd'
  </code></pre>
  
  <p>In the example the tolerance would be 0.1.</p>
  
  <p>Is this possible with pandas while specifying some tolerance to account for float problems?</p>
  
  <p>Of course, I could iterate, but usually, that is wrong when using pandas.</p>