# LOF
# 函数简介
本函数使用局部离群点检测方法用于查找序列的密度异常。将根据提供的第k距离数及局部离群点因子(lof)阈值，判断输入数据是否为离群点，即异常，并输出各点的LOF值。
函数名： LOF
输入序列： 多个输入序列，类型为 INT32 / INT64 / FLOAT / DOUBLE
参数：
method:使用的检测方法。默认为default，以高维数据计算。设置为series，将一维时间序列转换为高维数据计算。k:使用第k距离计算局部离群点因子.默认为3。window:每次读取数据的窗口长度。默认为10000.windowsize:使用series方法时，转化高维数据的维数，即单个窗口的大小。默认为5。
输出序列： 输出单时间序列，类型为DOUBLE。
提示： 不完整的数据行会被忽略，不参与计算，也不标记为离群点。
# 使用示例
# 默认参数
输入序列：
+-----------------------------+---------------+---------------+
| Time|root.test.d1.s1|root.test.d1.s2|
+-----------------------------+---------------+---------------+
|1970-01-01T08:00:00.100+08:00| 0.0| 0.0|
|1970-01-01T08:00:00.200+08:00| 0.0| 1.0|
|1970-01-01T08:00:00.300+08:00| 1.0| 1.0|
|1970-01-01T08:00:00.400+08:00| 1.0| 0.0|
|1970-01-01T08:00:00.500+08:00| 0.0| -1.0|
|1970-01-01T08:00:00.600+08:00| -1.0| -1.0|
|1970-01-01T08:00:00.700+08:00| -1.0| 0.0|
|1970-01-01T08:00:00.800+08:00| 2.0| 2.0|
|1970-01-01T08:00:00.900+08:00| 0.0| null|
+-----------------------------+---------------+---------------+
查询语句：
select lof(s1,s2) from root.test.d1 where time<1000
输出序列：
+-----------------------------+-------------------------------------+
| Time|lof(root.test.d1.s1, root.test.d1.s2)|
+-----------------------------+-------------------------------------+
|1970-01-01T08:00:00.100+08:00| 3.8274824267668244|
|1970-01-01T08:00:00.200+08:00| 3.0117631741126156|
|1970-01-01T08:00:00.300+08:00| 2.838155437762879|
|1970-01-01T08:00:00.400+08:00| 3.0117631741126156|
|1970-01-01T08:00:00.500+08:00| 2.73518261244453|
|1970-01-01T08:00:00.600+08:00| 2.371440975708148|
|1970-01-01T08:00:00.700+08:00| 2.73518261244453|
|1970-01-01T08:00:00.800+08:00| 1.7561416374270742|
+-----------------------------+-------------------------------------+
# 诊断一维时间序列
输入序列：
+-----------------------------+---------------+
| Time|root.test.d1.s1|
+-----------------------------+---------------+
|1970-01-01T08:00:00.100+08:00| 1.0|
|1970-01-01T08:00:00.200+08:00| 2.0|
|1970-01-01T08:00:00.300+08:00| 3.0|
|1970-01-01T08:00:00.400+08:00| 4.0|
|1970-01-01T08:00:00.500+08:00| 5.0|
|1970-01-01T08:00:00.600+08:00| 6.0|
|1970-01-01T08:00:00.700+08:00| 7.0|
|1970-01-01T08:00:00.800+08:00| 8.0|
|1970-01-01T08:00:00.900+08:00| 9.0|
|1970-01-01T08:00:01.000+08:00| 10.0|
|1970-01-01T08:00:01.100+08:00| 11.0|
|1970-01-01T08:00:01.200+08:00| 12.0|
|1970-01-01T08:00:01.300+08:00| 13.0|
|1970-01-01T08:00:01.400+08:00| 14.0|
|1970-01-01T08:00:01.500+08:00| 15.0|
|1970-01-01T08:00:01.600+08:00| 16.0|
|1970-01-01T08:00:01.700+08:00| 17.0|
|1970-01-01T08:00:01.800+08:00| 18.0|
|1970-01-01T08:00:01.900+08:00| 19.0|
|1970-01-01T08:00:02.000+08:00| 20.0|
+-----------------------------+---------------+
查询语句：
select lof(s1, "method"="series") from root.test.d1 where time<1000
输出序列：
+-----------------------------+--------------------+
| Time|lof(root.test.d1.s1)|
+-----------------------------+--------------------+
|1970-01-01T08:00:00.100+08:00| 3.77777777777778|
|1970-01-01T08:00:00.200+08:00| 4.32727272727273|
|1970-01-01T08:00:00.300+08:00| 4.85714285714286|
|1970-01-01T08:00:00.400+08:00| 5.40909090909091|
|1970-01-01T08:00:00.500+08:00| 5.94999999999999|
|1970-01-01T08:00:00.600+08:00| 6.43243243243243|
|1970-01-01T08:00:00.700+08:00| 6.79999999999999|
|1970-01-01T08:00:00.800+08:00| 7.0|
|1970-01-01T08:00:00.900+08:00| 7.0|
|1970-01-01T08:00:01.000+08:00| 6.79999999999999|
|1970-01-01T08:00:01.100+08:00| 6.43243243243243|
|1970-01-01T08:00:01.200+08:00| 5.94999999999999|
|1970-01-01T08:00:01.300+08:00| 5.40909090909091|
|1970-01-01T08:00:01.400+08:00| 4.85714285714286|
|1970-01-01T08:00:01.500+08:00| 4.32727272727273|
|1970-01-01T08:00:01.600+08:00| 3.77777777777778|
+-----------------------------+--------------------+