CODEWITHSUNDEEP
dataframeapache-sparkpysparkapache-spark-sql
Maher HTB
Maher HTB

Reputation: 737

Count the number of missing values in a dataframe Spark

I have a dataset with missing values , I would like to get the number of missing values for each columns. Following is what I did , I got the number of non missing values. How can I use it to get the number of missing values?

df.describe().filter($"summary" === "count").show

+-------+---+---+---+
|summary|  x|  y|  z|
+-------+---+---+---+
|  count|  1|  2|  3|
+-------+---+---+---+

Any help please to get a dataframe in which we'll find columns and number of missing values for each one.

Upvotes: 11

Views: 30789

Answers (3)

hailathamzeh
hailathamzeh

Reputation: 1

for i in df.columns:
  print(i,df.count()-(df.na.drop(subset=i).count()))

Upvotes: 0

Harish Vasudev
Harish Vasudev

Reputation: 21

from pyspark.sql.functions import isnull, when, count, col
nacounts = df.select([count(when(isnull(c), c)).alias(c) for c in df.columns]).toPandas()
nacounts

Upvotes: 2

mtoto
mtoto

Reputation: 24198

You could count the missing values by summing the boolean output of the isNull() method, after converting it to type integer:

In Scala:

import org.apache.spark.sql.functions.{sum, col}
df.select(df.columns.map(c => sum(col(c).isNull.cast("int")).alias(c)): _*).show

In Python:

from pyspark.sql.functions import col,sum
df.select(*(sum(col(c).isNull().cast("int")).alias(c) for c in df.columns)).show()

Alternatively, you could also use the output of df.describe().filter($"summary" === "count"), and subtract the number in each cell by the number of rows in the data:

In Scala:

import org.apache.spark.sql.functions.lit,

val rows = df.count()
val summary = df.describe().filter($"summary" === "count")
summary.select(df.columns.map(c =>(lit(rows) - col(c)).alias(c)): _*).show

In Python:

from pyspark.sql.functions import lit

rows = df.count()
summary = df.describe().filter(col("summary") == "count")
summary.select(*((lit(rows)-col(c)).alias(c) for c in df.columns)).show()

Upvotes: 29

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