Chart Patterns

Swing lows at 100 (day 4) and 104 (day 12) define a line rising 0.5 a day. Projected to day 20 it gives 108, and the third low lands exactly there: the line held. On day 24 the line is at 110, and the close of 113 is above it.

• Two points always make a line; only the third touch tests it, and which lows to connect is a judgement call.
• Steep lines break quickly, and their breaks say little.
• On growing assets a straight line on a price scale eventually breaks; a log scale gives a different line.

def swings(s, n=3):                     # a swing high (low) is the extreme of the 2n+1 bars around it
    w = s.rolling(2 * n + 1, center=True)
    return s[s == w.max()], s[s == w.min()]
c = df['close']
highs, lows = swings(c)
(x1, y1), (x2, y2) = list(lows.iloc[:2].items())      # the first two rising lows
slope = (y2 - y1) / (x2 - x1)
line = lambda x: y1 + slope * (x - x1)
x3, y3 = lows.index[2], lows.iloc[2]                  # the third low tests the line
held = y3 >= line(x3) * 0.99
broken = c.iloc[-1] < line(len(c) - 1)

Assumes import numpy as np, import pandas as pd, and a DataFrame df with columns open, high, low and close for the data above.