plot.py

import matplotlib.pyplot as plt
import matplotlib.ticker as ticker
from algs import find_maximum_subarray

def plot_regions(data, symbol):
    gain = find_maximum_subarray(data.change)
    loss = find_maximum_subarray(-data.change)
    
    fig, ax = plt.subplots()
    data.adj_close.plot()

    # add dollar sign to y axis labels
    formatter = ticker.FormatStrFormatter('$%.f')
    ax.yaxis.set_major_formatter(formatter)

    # put dollar amount labels on the right
    ax.tick_params(left=False, right=True)
    for tick in ax.yaxis.get_major_ticks():
        tick.label1On = False
        tick.label2On = True

    # add highlight box for hold period
    plt.axvspan(data.index[gain['low']-1], data.index[gain['high']], color='green', alpha=0.2)
    plt.axvspan(data.index[loss['low']-1], data.index[loss['high']], color='red', alpha=0.2)
    plt.title(f'{symbol}, gain = \${gain["sum"]:.2f}, loss = \${loss["sum"]:.2f}')

    plt.savefig('test.svg')
    plt.show()