stack_plot

def stack_plot(title, ylabel, dates, val_pairs, ymax=None, legend=None):
  # get series values
  fig, ax = plt.subplots(1,1)
  fig.set_figwidth(20)
  fig.set_figheight(10)
  ax.set_title(title, size=20)
  ax.set_ylabel(ylabel, size=20)
  ax.set_xlim((0, len(dates)))
  ax.minorticks_on()
  ax.grid(which='major', axis='y', linestyle='-', linewidth=2, color='k')
  ax.grid(which='minor', axis='y', linestyle='-', linewidth=1, color='.8')
  ax.set_axisbelow(True)
  ax.tick_params(axis='y', labelsize=16)
  totals = np.zeros(len(dates))
  for values, label in val_pairs:
    ax.bar(np.arange(len(dates))+.5, values, label=label, bottom=totals)
    totals += values
  date_ticks = np.arange(0, len(dates), 7)
  date_labels = dates[date_ticks]
  ax.set_xticklabels(date_labels, size=16, rotation=0, horizontalalignment='center')
  ax.set_xticks(date_ticks + .5)
  if ymax:
    ax.set_ylim((0, ymax))
  if legend:
    ncol, size, loc = legend
    handles, labels = ax.get_legend_handles_labels()
    ax.legend(handles[::-1], labels[::-1], loc=loc, fontsize=size, ncol=ncol, framealpha=1.)
  else:
    handles, labels = ax.get_legend_handles_labels()
    ax.legend(handles[::-1], labels[::-1], loc='upper left', fontsize=16, framealpha=1.)