title: select a specific range from a numpy 2d array to plot values
body: <p>for example with a numpy array like the following,</p>
  
  <p>a=([1,2,3,4,5], [100,200,300,400,500]) and x=a[0] and y=a[1] </p>
  
  <p>how can I plot xy where 2 &lt; x &lt; 4 ?</p>