title: How to combine a dataframe containing previous values ​with data frames containing current values?
body: <p>I have two data frames with matching indexes and columns. (30 columns).</p>
  <p>index: <strong>time and day</strong>.</p>
  <p>first dataframe:</p>
  <pre><code>time    day       200-approve-packages   200-delivered-packages     ...
  10.15   sunday    158                    112                        
  10:30   sunday    200                    110                        
  10:45   sunday    158                    145                        
  11:00   sunday    180                    170                        
  ...
  </code></pre>
  <p>and second:</p>
  <pre><code>time    day      200-approve-packages   200-delivered-packages     ...
  10.15   sunday   198                    117
  10:30   sunday   400                    200
  10:45   sunday   154                    178
  11:00   sunday   100                    200
  ...
  </code></pre>
  <p>the output should be like this:</p>
  <pre><code>time    day      200-approve-packages   previous-200-approve-packages    200-delivered-packages   previous-200-delivered-packages
  10.15   sunday   198                    158                              117                      112
  10:30   sunday   400                    200                              200                      110
  10:45   sunday   154                    158                              178                      145
  11:00   sunday   100                    180                              200                      170
  ...
  </code></pre>
  <p>the first data frame contains <strong>previous</strong> values ​​and the second data frame contains <strong>current</strong> values. is there a way to keep them understandably in a single data frame?</p>