Adding a new column in Data Frame derived from other columns (Spark)

One way to achieve that is to use withColumn method:

old_df = sqlContext.createDataFrame(sc.parallelize(
    [(0, 1), (1, 3), (2, 5)]), ('col_1', 'col_2'))

new_df = old_df.withColumn('col_n', old_df.col_1 - old_df.col_2)

Alternatively you can use SQL on a registered table:

old_df.registerTempTable('old_df')
new_df = sqlContext.sql('SELECT *, col_1 - col_2 AS col_n FROM old_df')