content: import matplotlib.pyplot as plt
  from collections import Counter
  
  def make_chart_simple_line_chart(plt):
  
      years = [1950, 1960, 1970, 1980, 1990, 2000, 2010]
      gdp = [300.2, 543.3, 1075.9, 2862.5, 5979.6, 10289.7, 14958.3]
  
      # create a line chart, years on x-axis, gdp on y-axis
      plt.plot(years, gdp, color='green', marker='o', linestyle='solid')
  
      # add a title
      plt.title("Nominal GDP")
  
      # add a label to the y-axis
      plt.ylabel("Billions of $")
      plt.show()
  
  
  def make_chart_simple_bar_chart(plt):
  
      movies = ["Annie Hall", "Ben-Hur", "Casablanca", "Gandhi", "West Side Story"]
      num_oscars = [5, 11, 3, 8, 10]
  
      # bars are by default width 0.8, so we'll add 0.1 to the left coordinates
      # so that each bar is centered
      xs = [i + 0.1 for i, _ in enumerate(movies)]
  
      # plot bars with left x-coordinates [xs], heights [num_oscars]
      plt.bar(xs, num_oscars)
      plt.ylabel("# of Academy Awards")
      plt.title("My Favorite Movies")
  
      # label x-axis with movie names at bar centers
      plt.xticks([i + 0.5 for i, _ in enumerate(movies)], movies)
      
      plt.show()
  
  def make_chart_histogram(plt):
      grades = [83,95,91,87,70,0,85,82,100,67,73,77,0]
      decile = lambda grade: grade // 10 * 10 
      histogram = Counter(decile(grade) for grade in grades)
  
      plt.bar([x - 4 for x in histogram.keys()], # shift each bar to the left by 4
              histogram.values(),                # give each bar its correct height
              8)                                 # give each bar a width of 8
      plt.axis([-5, 105, 0, 5])                  # x-axis from -5 to 105,
                                                 # y-axis from 0 to 5
      plt.xticks([10 * i for i in range(11)])    # x-axis labels at 0, 10, ..., 100
      plt.xlabel("Decile")
      plt.ylabel("# of Students")
      plt.title("Distribution of Exam 1 Grades")
      plt.show()
  
  def make_chart_misleading_y_axis(plt, mislead=True):
  
      mentions = [500, 505]
      years = [2013, 2014]
  
      plt.bar([2012.6, 2013.6], mentions, 0.8)
      plt.xticks(years)
      plt.ylabel("# of times I heard someone say 'data science'")
  
      # if you don't do this, matplotlib will label the x-axis 0, 1
      # and then add a +2.013e3 off in the corner (bad matplotlib!)
      plt.ticklabel_format(useOffset=False)
  
      if mislead:
          # misleading y-axis only shows the part above 500
          plt.axis([2012.5,2014.5,499,506])
          plt.title("Look at the 'Huge' Increase!")
      else:
          plt.axis([2012.5,2014.5,0,550])
          plt.title("Not So Huge Anymore.")       
      plt.show()
  
  def make_chart_several_line_charts(plt):
  
      variance     = [1,2,4,8,16,32,64,128,256]
      bias_squared = [256,128,64,32,16,8,4,2,1]
      total_error  = [x + y for x, y in zip(variance, bias_squared)]
  
      xs = range(len(variance))
  
      # we can make multiple calls to plt.plot 
      # to show multiple series on the same chart
      plt.plot(xs, variance,     'g-',  label='variance')    # green solid line
      plt.plot(xs, bias_squared, 'r-.', label='bias^2')      # red dot-dashed line
      plt.plot(xs, total_error,  'b:',  label='total error') # blue dotted line
  
      # because we've assigned labels to each series
      # we can get a legend for free
      # loc=9 means "top center"
      plt.legend(loc=9)
      plt.xlabel("model complexity")
      plt.title("The Bias-Variance Tradeoff")
      plt.show()
  
  def make_chart_scatter_plot(plt):
  
      friends = [ 70, 65, 72, 63, 71, 64, 60, 64, 67]
      minutes = [175, 170, 205, 120, 220, 130, 105, 145, 190]
      labels = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
  
      plt.scatter(friends, minutes)
      
      # label each point
      for label, friend_count, minute_count in zip(labels, friends, minutes):
          plt.annotate(label,
                       xy=(friend_count, minute_count), # put the label with its point
                       xytext=(5, -5), # but slightly offset
                       textcoords='offset points')
  
      plt.title("Daily Minutes vs. Number of Friends")
      plt.xlabel("# of friends")
      plt.ylabel("daily minutes spent on the site")
      plt.show()
  
  def make_chart_scatterplot_axes(plt, equal_axes=False):
  
      test_1_grades = [ 99, 90, 85, 97, 80]
      test_2_grades = [100, 85, 60, 90, 70]
  
      plt.scatter(test_1_grades, test_2_grades)
      plt.xlabel("test 1 grade")
      plt.ylabel("test 2 grade")
  
      if equal_axes:
          plt.title("Axes Are Comparable")
          plt.axis("equal")
      else:
          plt.title("Axes Aren't Comparable")
  
      plt.show()
  
  def make_chart_pie_chart(plt):
  
      plt.pie([0.95, 0.05], labels=["Uses pie charts", "Knows better"])
  
      # make sure pie is a circle and not an oval
      plt.axis("equal")
      plt.show()
  
  
  if __name__ == "__main__":
  
      make_chart_simple_line_chart(plt)
  
      make_chart_simple_bar_chart(plt)
  
      make_chart_histogram(plt)
  
      make_chart_misleading_y_axis(plt, mislead=True)
  
      make_chart_misleading_y_axis(plt, mislead=False)
  
      make_chart_several_line_charts(plt)
  
      make_chart_scatterplot_axes(plt, equal_axes=False)
  
      make_chart_scatterplot_axes(plt, equal_axes=True)
  
      make_chart_pie_chart(plt)
  