title: Making a Bokeh Heat map with a 20 x 1000 numpy array
body: <p>My Goal is to make a heat map like this one <img src="https://i.stack.imgur.com/W85JZ.png" alt="bokeh heatmap"></p>
  
  <p>The only difference is my array is much larger 30x3000. It seems like bokeh should be able to handle something like this but when I try I get something that looks like this: <img src="https://i.stack.imgur.com/gyeC3.png" alt="my version with large numpy array">.</p>
  
  <p>If I zoom in a lot I can start to see the color coding but I would like it to not look like that at first pass. </p>
  
  <p>I am new to Bokeh but it seems like something quite trivial. I usually use imshow in python. But, am trying to switch over.  </p>
  
  <p>EDIT: Here is the code: </p>
  
  <pre><code>from bokeh._legacy_charts import HeatMap, output_file, show
  
  xyvalues = np.random.random((28,1000))
  
  df = pd.DataFrame(xyvalues)
  
  output_file('heatmap.html')
  
  hm = HeatMap(df)
  
  show(hm)
  </code></pre>