title: Create conditional column for Date Difference based on matching values in two columns
body: <p>I have a dataframe, I am struggling to create a column based out of other columns, I will share the problem for a sample data.</p>
  
  <pre><code>        Date    Target1        Close
  0   2019-04-17  209.2440    203.130005
  1   2019-04-17  212.2155    203.130005
  2   2019-04-17  213.6330    203.130005
  3   2019-04-17  213.0555    203.130005
  4   2019-04-17  212.6250    203.130005
  5   2019-04-17  212.9820    203.130005
  6   2019-04-17  213.1395    203.130005
  7   2019-04-16  209.2860    199.250000
  8   2019-04-16  209.9055    199.250000
  9   2019-04-16  210.3045    199.250000
  </code></pre>
  
  <p>I want to create another column (for each observation) (called <code>days_to_hit_target</code> for example) which is the difference of days such that close hits (or comes very close to target of specific day), when it does closes that very closely, then it counts the difference of days and put them in the column days_to_hit_target.</p>