Lernen Handling Datetime Features

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The flights dataset stores date information across three separate integer columns – YEAR, MONTH, and DAY. Combining them into a proper date and extracting meaningful components is a common feature engineering step.

Building a Date Column


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import urllib.request
from pyspark.sql import SparkSession
from pyspark.sql.functions import col, concat_ws, lpad, to_date, dayofweek, month, quarter, dayofyear

urllib.request.urlretrieve(
    "https://staging-content-media-cdn.codefinity.com/courses/aa80ac56-0d50-49e8-9231-2c2374cd3e9d/flights.csv",
    "flights.csv"
)

spark = SparkSession.builder \
    .appName("DatetimeFeatures") \
    .master("local[*]") \
    .getOrCreate()

flights_df = spark.read.csv("flights.csv", header=True, inferSchema=True) \
    .fillna(0, subset=["DEPARTURE_DELAY", "ARRIVAL_DELAY"])

# Combining YEAR, MONTH, DAY into a DateType column
flights_df = flights_df.withColumn(
    "FLIGHT_DATE",
    to_date(
        concat_ws("-",
            col("YEAR").cast("string"),
            lpad(col("MONTH").cast("string"), 2, "0"),
            lpad(col("DAY").cast("string"), 2, "0")
        ),
        "yyyy-MM-dd"
    )
)

flights_df.select("YEAR", "MONTH", "DAY", "FLIGHT_DATE").show(5)

Extracting Date Components

Once you have a proper DateType column, PySpark provides built-in functions to extract components:


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# Extracting useful date components as separate feature columns
flights_df = flights_df \
    .withColumn("MONTH_NUM", month(col("FLIGHT_DATE"))) \
    .withColumn("QUARTER", quarter(col("FLIGHT_DATE"))) \
    .withColumn("DAY_OF_YEAR", dayofyear(col("FLIGHT_DATE")))

flights_df.select("FLIGHT_DATE", "MONTH_NUM", "QUARTER", "DAY_OF_YEAR").show(5)

Cyclic Encoding for Month and Hour

Month and hour are cyclic – December is close to January, and 23:00 is close to 00:00. Encoding them as raw integers loses this property. Sine and cosine encoding preserves it:


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import pyspark.sql.functions as F
import math

# Encoding month cyclically so that month 12 is close to month 1
flights_df = flights_df \
    .withColumn("MONTH_SIN", F.sin(2 * math.pi * col("MONTH_NUM") / 12)) \
    .withColumn("MONTH_COS", F.cos(2 * math.pi * col("MONTH_NUM") / 12))

flights_df.select("MONTH_NUM", "MONTH_SIN", "MONTH_COS").distinct().orderBy("MONTH_NUM").show()

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Abschnitt 1. Kapitel 8

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Abschnitt 1. Kapitel 8