[Python] time as sine cosine values

import numpy as np
import pandas as pd

def rand_times(n):
    """Generate n rows of random 24-hour times (seconds past midnight)"""
    rand_seconds = np.random.randint(0, 24*60*60, n)
    return pd.DataFrame(data=dict(seconds=rand_seconds))

# Create raw data
n_rows = 1000

df = rand_times(n_rows)
# sort for the sake of graphing
df = df.sort_values('seconds').reset_index(drop=True)
df.seconds.plot()

# Sine & cosine transform
seconds_in_day = 24*60*60

df['sin_time'] = np.sin(2*np.pi*df.seconds/seconds_in_day)
df['cos_time'] = np.cos(2*np.pi*df.seconds/seconds_in_day)

df.drop('seconds', axis=1, inplace=True)

# Combine the two yield a cyclical pattern
df.sin_time.plot()
df.cos_time.plot()
df.sample(30).plot.scatter('sin_time','cos_time').set_aspect('equal')