title: Count cases by dates and save it in a new dataframe
body: <p>In one data frame (called X) I have <code>Patient_admitted_id</code>, <code>Date</code>, <code>Hospital_ID</code> of tested covid positive patients (I show this data frame below). I want to generate a separated data frame (called Y) with <code>Dates</code> of the calendar, total number of covid <code>Cases</code> and <code>cumulative</code> cases.</p>
  <p>I dont know how to generate the column <code>Cases</code></p>
  <p>X data frame:</p>
  <pre><code>data = {'Patient_admitted_id': [214321,224323,3234234,23423],
          'Date':  ['2021-01-22', '2021-01-22','2021-01-22','2021-01-20'], # This is just an example I have created here, the real X data frame contains proper date values generated with Datatime
          'Hospital_ID': ['1', '2','3','2'],
          }
  X = pd.DataFrame(data, columns=['Patient_admitted_id','Date', 'Hospital_ID' ])
  X
      Patient_admitted_id     Date    Hospital_ID
  0   214321               2021-01-22     1
  1   224323               2021-01-22     2
  2   3234234              2021-01-22     3
  3   23423                2021-01-20     2
  ...
  </code></pre>
  <p>Desirable Y data frame:</p>
  <pre><code>    Date        Cases    Cumulative
  0   2021-01-20    1         1           
  1   2021-01-21    0         1         
  2   2021-01-22    3         4     
  ...
  </code></pre>