title: Trying to plot and regroup 2 dataframes
body: <p>Here is my code : </p>
  
  <pre><code>import pandas as pd
  import io
  data="""
  ;Barcode;Created;Hash;Modified;Tag;Tag2
  0;9780735711020;2019-02-22T22:35:06.628Z;None;2019-02-22T22:35:06.628Z;NEED_PICS;
  1;3178041328890;2019-02-22T22:37:44.546Z;None;2019-02-22T22:37:44.546Z;DISPLAY;
  2;8718951129597;2019-02-23T04:53:17.925Z;None;2019-02-23T04:53:17.925Z;DISPLAY;
  3;3770006053078;2019-02-23T05:25:56.454Z;None;2019-02-23T05:25:56.454Z;DISPLAY;
  4;3468080404892;2019-02-23T05:26:39.923Z;None;2019-02-23T05:26:39.923Z;NEED_PICS;
  5;3517360013757;2019-02-23T05:27:24.910Z;None;2019-02-23T05:27:24.910Z;DISPLAY;
  6;3464660000768;2019-02-23T05:27:51.379Z;None;2019-02-23T05:27:51.379Z;DISPLAY;
  7;30073357;2019-02-23T06:20:53.075Z;None;2019-02-23T06:20:53.075Z;NEED_PICS;
  8;02992;2019-02-23T06:22:57.326Z;None;2019-02-23T06:22:57.326Z;NEED_PICS;
  9;3605532558776;2019-02-23T06:23:45.010Z;None;2019-02-23T06:23:45.010Z;NEED_PICS;
  10;3605532558776;2019-02-23T06:23:48.291Z;None;2019-02-23T06:23:48.291Z;NEED_PICS;
  11;3605532558776;2019-02-23T06:23:52.579Z;None;2019-02-23T06:23:52.579Z;NEED_PICS;
  """
  from io import StringIO
  TESTDATA = StringIO(data)
  
  df = pd.read_csv(TESTDATA, sep=";")
  df["Created"] = pd.to_datetime(df["Created"],errors='coerce')
  df["Barcode"] = df["Barcode"].astype(str)
  df.set_index(df.columns[0], inplace=True)
  df2 = df #df[df.Hash != "None"]
  df3 = df2
  df3 = df3.loc[df3.Tag == "DISPLAY"]
  df = df2.merge(df3, on='Created', how='outer').fillna(0)
  df['sum'] = df['Barcode_x']+df['Barcode_y']
  df.plot(df['sum'], df['Created'])
  </code></pre>
  
  <p>So i'am trying at the end to plot, two line graph on the same plot.</p>
  
  <p>I would like to have regrouped by day the number of occurence for two dataframe df2 all Tag , and df3 with just the tag display.</p>
  
  <p>And i would like to plot 2 line in the same graph one with all occurence by day with all the time and one with occurence of just the tag display.</p>
  
  <p>For the moment i only managed to get this  :</p>
  
  <p><a href="https://i.stack.imgur.com/3AABl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3AABl.png" alt="enter image description here"></a></p>