title: Heatmap in python to represent (x,y) coordinates in a given rectangular area
body: <p>Let's say we have x,y coordinates as an input where x is in range(0,300) &amp; y is in range(0,400)
  I want to plot all of these coordinates as a heat map in a rectangular grid of width between (0,300) &amp; height between (0,400).</p>
  
  <p>Using seaborn, or matplotlib, I'm able to plot a scatter plot, but struggling to plot these points as a heatmap.</p>
  
  <pre><code>x = numpy.random.randint(0, high=50, size=5000, dtype='l')
  y = numpy.random.randint(0, high=50, size=5000, dtype='l')
  </code></pre>
  
  <p>Thus, if my sample size is 5000 points &amp; all are nearly in the range of x as (0,50) &amp; y as (0,50) representing them in a rectangular space of 300x400 should demonstrate the highest density of coordinates in 50x50 space.</p>
  
  <p>Can someone please guide me how to represent this data?</p>
  
  <p>For testing &amp; plotting on scatter plot, I used seaborn's lmplot function.</p>
  
  <pre><code>df = pd.DataFrame()
  
  df['x'] = pd.Series(numpy.random.randint(0, high=320, size=5000, dtype='l'))
  df['y'] = pd.Series(numpy.random.randint(0, high=480, size=5000, dtype='l'))
  sns.set_style('whitegrid')
  sns.lmplot('x','y',data=df,
         palette='coolwarm',size=10,fit_reg=False)
  plt.show()
  </code></pre>