val df = Range(0,10,step=1).toDF("id").withColumn("rand1", rand(seed=10)).withColumn("rand2", rand(seed=27))
df: org.apache.spark.sql.DataFrame = [id: int, rand1: double ... 1 more field]

df.show
+---+-------------------+-------------------+
| id|              rand1|              rand2|
+---+-------------------+-------------------+
|  0|0.41371264720975787|  0.714105256846827|
|  1| 0.7311719281896606| 0.8143487574232506|
|  2| 0.9031701155118229| 0.5282207324381174|
|  3|0.09430205113458567| 0.4420100497826609|
|  4|0.38340505276222947| 0.9387162206758006|
|  5| 0.5569246135523511| 0.6398126862647711|
|  6| 0.4977441406613893| 0.9895498513115722|
|  7| 0.2076666106201438| 0.3398720242725498|
|  8| 0.9571919406508957|0.15042237695815963|
|  9| 0.7429395461204413| 0.7302723457066639|
+---+-------------------+-------------------+


df.stat.corr("rand1", "rand2", "pearson")
res24: Double = -0.10993962467082698

val colArray = Array("age", "yearsmarried", "religiousness", "education", "occupation", "rating")

// 查看数据的统计分布情况
val descrDF = data.describe("age", "yearsmarried", "religiousness", "education", "occupation", "rating")
descrDF: org.apache.spark.sql.DataFrame = [summary: string, age: string ... 5 more fields]

descrDF.selectExpr("summary",
        "round(age,2) as age",
        "round(yearsmarried,2) as yearsmarried",
        "round(religiousness,2) as religiousness",
        "round(education,2) as education",
        "round(occupation,2) as occupation",
        "round(rating,2) as rating").show(10, truncate = false)
+-------+-----+------------+-------------+---------+----------+------+
|summary|age  |yearsmarried|religiousness|education|occupation|rating|
+-------+-----+------------+-------------+---------+----------+------+
|count  |601.0|601.0       |601.0        |601.0    |601.0     |601.0 |
|mean   |32.49|8.18        |3.12         |16.17    |4.19      |3.93  |
|stddev |9.29 |5.57        |1.17         |2.4      |1.82      |1.1   |
|min    |17.5 |0.13        |1.0          |9.0      |1.0       |1.0   |
|max    |57.0 |15.0        |5.0          |20.0     |7.0       |5.0   |
+-------+-----+------------+-------------+---------+----------+------+

// 统计字段中元素的个数
val fi = data.stat.freqItems(colArray)
fi: org.apache.spark.sql.DataFrame = [age_freqItems: array<double>, yearsmarried_freqItems: array<double> ... 4 more fields]

fi.printSchema()
root
 |-- age_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)
 |-- yearsmarried_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)
 |-- religiousness_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)
 |-- education_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)
 |-- occupation_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)
 |-- rating_freqItems: array (nullable = true)
 |    |-- element: double (containsNull = false)


val f = fi.selectExpr(
     |   "size(age_freqItems)",
     |   "size(yearsmarried_freqItems)",
     |   "size(religiousness_freqItems)",
     |   "size(education_freqItems)",
     |   "size(occupation_freqItems)",
     |   "size(rating_freqItems)")
f: org.apache.spark.sql.DataFrame = [size(age_freqItems): int, size(yearsmarried_freqItems): int ... 4 more fields]

f.show(10, truncate = false)
+-------------------+----------------------------+-----------------------------+-------------------------+--------------------------+----------------------+
|size(age_freqItems)|size(yearsmarried_freqItems)|size(religiousness_freqItems)|size(education_freqItems)|size(occupation_freqItems)|size(rating_freqItems)|
+-------------------+----------------------------+-----------------------------+-------------------------+--------------------------+----------------------+
|9                  |8                           |5                            |7                        |7                         |5                     |
+-------------------+----------------------------+-----------------------------+-------------------------+--------------------------+----------------------+

// 集合字段的元素
val f1 = data.stat.freqItems(Array("age", "yearsmarried", "religiousness"))
f1: org.apache.spark.sql.DataFrame = [age_freqItems: array<double>, yearsmarried_freqItems: array<double> ... 1 more field]

f1.show(10, truncate = false)
+------------------------------------------------------+-----------------------------------------------+-------------------------+
|age_freqItems                                         |yearsmarried_freqItems                         |religiousness_freqItems  |
+------------------------------------------------------+-----------------------------------------------+-------------------------+
|[32.0, 47.0, 22.0, 52.0, 37.0, 17.5, 27.0, 57.0, 42.0]|[0.75, 0.125, 1.5, 0.417, 4.0, 7.0, 10.0, 15.0]|[2.0, 5.0, 4.0, 1.0, 3.0]|
+------------------------------------------------------+-----------------------------------------------+-------------------------+


// 对数组的元素排序

f1.selectExpr("sort_array(age_freqItems)", "sort_array(yearsmarried_freqItems)", "sort_array(religiousness_freqItems)").show(10, truncate = false)
+------------------------------------------------------+-----------------------------------------------+-----------------------------------------+
|sort_array(age_freqItems, true)                       |sort_array(yearsmarried_freqItems, true)       |sort_array(religiousness_freqItems, true)|
+------------------------------------------------------+-----------------------------------------------+-----------------------------------------+
|[17.5, 22.0, 27.0, 32.0, 37.0, 42.0, 47.0, 52.0, 57.0]|[0.125, 0.417, 0.75, 1.5, 4.0, 7.0, 10.0, 15.0]|[1.0, 2.0, 3.0, 4.0, 5.0]                |
+------------------------------------------------------+-----------------------------------------------+-----------------------------------------+




// 集合字段的元素
val f2 = data.stat.freqItems(Array("education", "occupation", "rating"))
f2: org.apache.spark.sql.DataFrame = [education_freqItems: array<double>, occupation_freqItems: array<double> ... 1 more field]

f2.show(10, truncate = false)
+-----------------------------------------+-----------------------------------+-------------------------+
|education_freqItems                      |occupation_freqItems               |rating_freqItems         |
+-----------------------------------------+-----------------------------------+-------------------------+
|[17.0, 20.0, 14.0, 16.0, 9.0, 18.0, 12.0]|[2.0, 5.0, 4.0, 7.0, 1.0, 3.0, 6.0]|[2.0, 5.0, 4.0, 1.0, 3.0]|
+-----------------------------------------+-----------------------------------+-------------------------+


// 对数组的元素排序
f2.selectExpr("sort_array(education_freqItems)", "sort_array(occupation_freqItems)", "sort_array(rating_freqItems)").show(10, truncate = false)
+-----------------------------------------+--------------------------------------+----------------------------------+
|sort_array(education_freqItems, true)    |sort_array(occupation_freqItems, true)|sort_array(rating_freqItems, true)|
+-----------------------------------------+--------------------------------------+----------------------------------+
|[9.0, 12.0, 14.0, 16.0, 17.0, 18.0, 20.0]|[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0]   |[1.0, 2.0, 3.0, 4.0, 5.0]         |
+-----------------------------------------+--------------------------------------+----------------------------------+