mean均值，variance方差，stddev标准差，corr(Pearson相关系数)，skewness偏度，kurtosis峰度
val df4=spark.sql("SELECT mean(age),variance(age),stddev(age),corr(age,yearsmarried),skewness(age),kurtosis(age) FROM Affairs")
df4.show
+--------+------------------+------------------+-----------------------+-----------------+--------------------+
|avg(age)| var_samp(age)| stddev_samp(age)|corr(age, yearsmarried)| skewness(age)| kurtosis(age)|
+--------+------------------+------------------+-----------------------+-----------------+--------------------+
| 34.0|173.33333333333334|13.165611772087667| 0.7456766124552038|0.965388004190285|-0.43417159763313595|
+--------+------------------+------------------+-----------------------+-----------------+--------------------+
