title: kivy garden Grap xmin xmax update (real time)
body: <p>is there a way to update xmin and xmax of Graph in kivy garden?</p>
  
  <p>At the moment, my xmin is 0 and xmax is 10 and I am plotting a list containin (x,y) points. y starts from 0 and is incremented every second and x is just a counter that counts iterations. so once x is > 10 the graph is not updated in real time so the x axis does not move like e.g. 1-11 and next second 2-12 and next 3-13 etc etc so I always show 10 values but the grap is 'live'.</p>
  
  <p>How to achieve it in kivy garden Graph?</p>
  
  <pre><code>   graph = Graph(
                      xlabel='Iteration',
                      ylabel='Value',
                      x_ticks_minor=1,
                      x_ticks_major=5,
                      y_ticks_major=1,
                      y_grid_label=True,
                      x_grid_label=True,
                      padding=5,
                      xlog=False,
                      ylog=False,
                      x_grid=True,
                      y_grid=True,
                      xmin=0,
                      xmax=10,
                      ymin=0,
                      ymax=11,
                      **graph_theme)
  </code></pre>