Pandas (28)

How to find all the local maxima (or peaks) in a numeric series?

# Input
ser = pd.Series([2, 10, 3, 4, 9, 10, 2, 7, 3])

# Solution
dd = np.diff(np.sign(np.diff(ser)))
peak_locs = np.where(dd == -2)[0] + 1
peak_locs

# output
array([1, 5, 7])