title: How to plot the derivative of a plot python?
body: <p>I use plotly to plot my data by using this function:</p>
  
  <pre><code>data_t = []
  
  for mac, dico_data in dict_info.items():
      data_t.append(go.Scatter( x= dico_data["time"], y= dico_data['val'], name=mac ))
      print (data_t)
  data = data_t
  offline.plot(data_t)
  </code></pre>
  
  <p>I need to use a set of data points from a graph to find a derivative and plot it. however I don't find how to do that ?
  This is an example of my data:</p>
  
  <pre><code>[Scatter({
      'name': '14:15:92:cc:00:00:00:01',
      'x': [707, 1212, 1616, 1818, 2020, 2121, 2323, 2424, 2525, 6969, 11009, 11716,
            12019, 16059, 16564, 19493, 20099, 23533, 23836, 25149, 29896, 43127,
            45147, 45753, 55045, 66761, 66862, 77467, 81204, 82921, 92718, 104434],
      'y': [1539071748.0, 1539071752.0, 1539071755.0, 1539071757.0, 1539071759.0,
            1539071760.0, 1539071764.0, 1539071765.0, 1539071768.0, 1539071872.0,
            1539071979.0, 1539071998.0, 1539072006.0, 1539072123.0, 1539072137.0,
            1539072226.0, 1539072250.0, 1539072386.0, 1539072398.0, 1539072450.0,
            1539072637.0, 1539073158.0, 1539073243.0, 1539073268.0, 1539073615.0,
            1539074097.0, 1539074101.0, 1539074533.0, 1539074691.0, 1539074763.0,
            1539075159.0, 1539075623.0]
  })]
  [Scatter({
      'name': '14:15:92:cc:00:00:00:01',
      'x': [707, 1212, 1616, 1818, 2020, 2121, 2323, 2424, 2525, 6969, 11009, 11716,
            12019, 16059, 16564, 19493, 20099, 23533, 23836, 25149, 29896, 43127,
            45147, 45753, 55045, 66761, 66862, 77467, 81204, 82921, 92718, 104434],
      'y': [1539071748.0, 1539071752.0, 1539071755.0, 1539071757.0, 1539071759.0,
            1539071760.0, 1539071764.0, 1539071765.0, 1539071768.0, 1539071872.0,
            1539071979.0, 1539071998.0, 1539072006.0, 1539072123.0, 1539072137.0,
            1539072226.0, 1539072250.0, 1539072386.0, 1539072398.0, 1539072450.0,
            1539072637.0, 1539073158.0, 1539073243.0, 1539073268.0, 1539073615.0,
            1539074097.0, 1539074101.0, 1539074533.0, 1539074691.0, 1539074763.0,
            1539075159.0, 1539075623.0]
  })
  </code></pre>