Making histogram with Spark DataFrame column

Question

I am trying to make a histogram with a column from a dataframe which looks like

DataFrame[C0: int, C1: int, ...]

If I were to make a histog

Answer 1

You can use histogram_numeric Hive UDAF:

import random

random.seed(323)

sqlContext = HiveContext(sc)
n = 3  # Number of buckets
df = sqlContext.createDataFrame(
    sc.parallelize(enumerate(random.random() for _ in range(1000))),
   ["id", "v"]
)

hists = df.selectExpr("histogram_numeric({0}, {1})".format("v", n))

hists.show(1, False)
## +------------------------------------------------------------------------------------+
## |histogram_numeric(v,3)                                                              |
## +------------------------------------------------------------------------------------+
## |[[0.2124888140177466,415.0], [0.5918851340384337,330.0], [0.8890271451209697,255.0]]|
## +------------------------------------------------------------------------------------+

You can also extract the column of interest and use histogram method on RDD:

df.select("v").rdd.flatMap(lambda x: x).histogram(n)
## ([0.002028109534323752,
##  0.33410233677189705,
##  0.6661765640094703,
##  0.9982507912470436],
## [327, 326, 347])