seasonal decompose in python
It looks like your freq is off.
import numpy as npimport pandas as pdfrom statsmodels.tsa.seasonal import seasonal_decompose# Generate some datanp.random.seed(0)n = 1500dates = np.array('2005-01-01', dtype=np.datetime64) + np.arange(n)data = 12*np.sin(2*np.pi*np.arange(n)/365) + np.random.normal(12, 2, 1500)df = pd.DataFrame({'data': data}, index=dates)# Reproduce the example in OPseasonal_decompose(df, model='additive', freq=1).plot()
# Redo the same thing, but with the known frequencyseasonal_decompose(df, model='additive', freq=365).plot()