title: Bokeh Plot Update Using Slider
body: <p>I am trying to use a slider to update my Bokeh Plot. I am finding it difficult to achieve it using pandas dataframe(did not find any examples so far).
  The other way is to use the "columndatasource" (found some examples over forums) but still not able to achieve the functionality.
  So I have two columns, X axis is date and the Y axis is Volume. I want to change my Y values based on slider input. I am able to see the plot but the slider functionality is not working</p>
  
  <p>Any help will be very much appreciable. </p>
  
  <pre><code>source = ColumnDataSource(data=dict(x=df2['Date'],y=df2['Vol']))
  S1 = figure(plot_width=400,plot_height=400,tools=TOOLS1,title="Volume Per Day",x_axis_type="datetime")
  S1.line('x','y',source=source)
  
  callback_test = CustomJS(args=dict(source=source), code="""
  var data = source.get('data');
  var s_val = cb_obj.value
  x = data['x']
  y = data['y']
  console.log(cb_obj) 
  for (i = 0; i &lt; s_val; i++) {
      y[i] = y[i]            
      }
  source.trigger('change');
  """)
  
  slider = Slider(start=0, end= max_Vol, value=1, step=100,title="Vol Per Day",callback=callback_test)
  </code></pre>