easter-stats.sage

## Returns the date of easter in Gregorian year y, where 0 = March 31
def easter(y):
    a = y%19
    b = y//100
    c = y%100
    d = b//4
    e = b%4
    f = (b+8)//25
    g = (b-f+1)//3
    h = (19*a+b-d-g+15)%30
    i = c//4
    k = c%4
    l = (32+2*e+2*i-h-k)%7
    m = (a+11*h+22*l)//451
    n = h+l-7*m+114
    return n-123

eastertab = [easter(i) for i in range(5700000)]
easterstats = [0 for j in range(35)]
for i in range(5700000):
    easterstats[eastertab[i]+9] += 1
easterbistats = [[0 for j in range(35)] for j2 in range(35)]
for i in range(5700000):
    easterbistats[eastertab[i]+9][eastertab[(i+1)%5700000]+9] += 1

import matplotlib.pyplot as plt
import numpy as np
frqtab = [[easterbistats[i][j]/5700000 for j in range(35)] for i in range(35)]
plt.pcolormesh([[i-9 for j in range(35)] for i in range(35)],[[j-9 for j in range(35)] for i in range(35)], frqtab, shading="nearest")
plt.savefig("/tmp/easter.png")