File:PDO.svg

from urllib.request import urlretrieve
url = 'http://research.jisao.washington.edu/pdo/'
file = 'PDO.latest' # Monthly PDO from 1900.
if input(f'''Refresh local copy from {url}?
non-empty input for YES '''): urlretrieve(url+file, file)
data = []
with open(file, 'r') as f:
    for line in f:
        if line.startswith('YEAR'): break
    f.readline()
    for line in f:
        if line == '\n': break
        data += line.split()[1:]
data = [float(_) for _ in data]
import numpy as np
x = 1900. + 1/24. + np.linspace(0., len(data)/12, len(data), endpoint=False)
n = 121
n2 = n//2
kernel = np.sin(np.pi*np.linspace(1/(n+1), 1., n, endpoint=False))
kernel /= np.sum(kernel)
av = np.convolve(data, kernel, mode='valid')
import matplotlib.pyplot as plt
plt.rcParams['svg.fonttype'] = 'none' # text as text, not curves
fig, ax = plt.subplots(figsize=(5,3))
ax.fill_between(x[n2:-n2], av, 0., where= av > 0., facecolor='red',  interpolate=True)
ax.fill_between(x[n2:-n2], av, 0., where= av < 0., facecolor='blue', interpolate=True)
ax.plot(x[n2:-n2], av, 'k-', linewidth=0.4)
ax.plot(x, data, 'ko', markerfacecolor='#00000060', markeredgecolor='#00000000', markersize=2)
ax.set_xlim(x[0]-2., x[-1]+2.)
fig.text(.52,.88, 'PDO Index', horizontalalignment='center', fontname='Verdana', fontsize=14)
fig.tight_layout()
fig.savefig('PDO.svg', format='svg')
fig.show()