title: Python Heatmap Table Coloring Issue
body: <p>I am trying to make a heatmap that can be read in html, it is currently outputting the data properly, but the heatmap coloring  is based off the max value in each column not on the max value in the data I am not sure how to go about changing this so the heatmap is based on all the data.   </p>
  
  <pre><code>from flask import *
  import pandas as pd
  import seaborn as sns
  
  app = Flask(__name__)
  
  @app.route("/Matrix")
  def show_tables():
      cm = sns.light_palette("red", as_cmap=True)
      df = pd.read_csv('matrix.csv', header=0, index_col=0, na_filter=False)
      df = df.sort_index(ascending=False)
      html = (df.style.background_gradient(cmap=cm).render())
      return render_template('view.html', tables=[html])
  if __name__ == "__main__":
      app.run(debug=True)
  </code></pre>
  
  <p>Heatmap Table Output:</p>
  
  <p><img src="https://i.stack.imgur.com/4kheL.png" alt="Heatmap Table Output"></p>