sparksql_统计每行缺失值_统计每列缺失值

df_miss = spark.createDataFrame([
        (1, 143.5, 5.6, 28,   'M',  100000),
        (2, 167.2, 5.4, 45,   'M',  None),
        (3, None , 5.2, None, None, None),
        (4, 144.5, 5.9, 33,   'M',  None),
        (5, 133.2, 5.7, 54,   'F',  None),
        (6, 124.1, 5.2, None, 'F',  None),
        (7, 129.2, 5.3, 42,   'M',  76000),
    ], ['id', 'weight', 'height', 'age', 'gender', 'income'])
To find the number of missing observations per row we can use the following snippet.

#统计每一行缺失的数据量
df_miss.rdd.map(
    lambda row: (row['id'], sum([c == None for c in row]))
).collect()
[(1, 0), (2, 1), (3, 4), (4, 1), (5, 1), (6, 2), (7, 0)]
Let's see what values are missing so when we count missing observations in columns we can decide whether to drop the observation altogether or impute some of the observations.

#第三行数据缺失有点多，来看一下第三行数据
df_miss.where('id == 3').show()
+---+------+------+----+------+------+
| id|weight|height| age|gender|income|
+---+------+------+----+------+------+
|  3|  null|   5.2|null|  null|  null|
+---+------+------+----+------+------+

What is the percentage of missing observations we see in each column?

#统计每列数据缺失情况
df_miss.agg(*[
    (1 - (fn.count(c) / fn.count('*'))).alias(c + '_missing')
    for c in df_miss.columns
]).show()
+----------+------------------+--------------+------------------+------------------+------------------+
|id_missing|    weight_missing|height_missing|       age_missing|    gender_missing|    income_missing|
+----------+------------------+--------------+------------------+------------------+------------------+
|       0.0|0.1428571428571429|           0.0|0.2857142857142857|0.1428571428571429|0.7142857142857143|
+----------+------------------+--------------+------------------+------------------+------------------+