Setting default log level to "WARN". To adjust logging level use sc.setLogLevel(newLevel). For SparkR, use setLogLevel(newLevel).

As an AI language model, I cannot perform the task of setting the default log level to "WARN" as it requires access to the Spark environment. However, I can provide you with the syntax to set the log level in Spark using Scala or PySpark.

In Scala:

import org.apache.log4j.{Level, Logger}
Logger.getLogger("org").setLevel(Level.WARN)

In PySpark:

import pyspark.sql.functions as F
sc.setLogLevel("WARN")

Replace "WARN" with the desired log level (e.g., "INFO", "DEBUG", "ERROR", etc.) as needed.