# LowPass
# Usage
This function performs low-pass filtering on the input series and extracts components below the cutoff frequency. The timestamps of input will be ignored and all data points will be regarded as equidistant.
Name: LOWPASS
Input: Only support a single input series. The type is INT32 / INT64 / FLOAT / DOUBLE.
Parameters:
wpass: The normalized cutoff frequency which values (0,1). This parameter cannot be lacked.
Output: Output a single series. The type is DOUBLE. It is the input after filtering. The length and timestamps of output are the same as the input.
Note: NaN in the input series will be ignored.
# Examples
Input series:
+-----------------------------+---------------+
| Time|root.test.d1.s1|
+-----------------------------+---------------+
|1970-01-01T08:00:00.000+08:00| 2.902113|
|1970-01-01T08:00:01.000+08:00| 1.1755705|
|1970-01-01T08:00:02.000+08:00| -2.1755705|
|1970-01-01T08:00:03.000+08:00| -1.9021131|
|1970-01-01T08:00:04.000+08:00| 1.0|
|1970-01-01T08:00:05.000+08:00| 1.9021131|
|1970-01-01T08:00:06.000+08:00| 0.1755705|
|1970-01-01T08:00:07.000+08:00| -1.1755705|
|1970-01-01T08:00:08.000+08:00| -0.902113|
|1970-01-01T08:00:09.000+08:00| 0.0|
|1970-01-01T08:00:10.000+08:00| 0.902113|
|1970-01-01T08:00:11.000+08:00| 1.1755705|
|1970-01-01T08:00:12.000+08:00| -0.1755705|
|1970-01-01T08:00:13.000+08:00| -1.9021131|
|1970-01-01T08:00:14.000+08:00| -1.0|
|1970-01-01T08:00:15.000+08:00| 1.9021131|
|1970-01-01T08:00:16.000+08:00| 2.1755705|
|1970-01-01T08:00:17.000+08:00| -1.1755705|
|1970-01-01T08:00:18.000+08:00| -2.902113|
|1970-01-01T08:00:19.000+08:00| 0.0|
+-----------------------------+---------------+
SQL for query:
select lowpass(s1,'wpass'='0.45') from root.test.d1
Output series:
+-----------------------------+----------------------------------------+
| Time|lowpass(root.test.d1.s1, "wpass"="0.45")|
+-----------------------------+----------------------------------------+
|1970-01-01T08:00:00.000+08:00| 1.9021130073323922|
|1970-01-01T08:00:01.000+08:00| 1.1755704705132448|
|1970-01-01T08:00:02.000+08:00| -1.1755705286582614|
|1970-01-01T08:00:03.000+08:00| -1.9021130389094498|
|1970-01-01T08:00:04.000+08:00| 7.450580419288145E-9|
|1970-01-01T08:00:05.000+08:00| 1.902113046743454|
|1970-01-01T08:00:06.000+08:00| 1.1755705212076808|
|1970-01-01T08:00:07.000+08:00| -1.1755704886020932|
|1970-01-01T08:00:08.000+08:00| -1.9021130222335536|
|1970-01-01T08:00:09.000+08:00| 3.552713678800501E-16|
|1970-01-01T08:00:10.000+08:00| 1.9021130222335536|
|1970-01-01T08:00:11.000+08:00| 1.1755704886020932|
|1970-01-01T08:00:12.000+08:00| -1.1755705212076801|
|1970-01-01T08:00:13.000+08:00| -1.902113046743454|
|1970-01-01T08:00:14.000+08:00| -7.45058112983088E-9|
|1970-01-01T08:00:15.000+08:00| 1.9021130389094498|
|1970-01-01T08:00:16.000+08:00| 1.1755705286582616|
|1970-01-01T08:00:17.000+08:00| -1.1755704705132448|
|1970-01-01T08:00:18.000+08:00| -1.9021130073323924|
|1970-01-01T08:00:19.000+08:00| -2.664535259100376E-16|
+-----------------------------+----------------------------------------+
Note: The input is