# ValueFill
# Usage
This function is used to impute time series. Several methods are supported.
Name: ValueFill Input Series: Only support a single input series. The type is INT32 / INT64 / FLOAT / DOUBLE.
Parameters:
method: {"mean", "previous", "linear", "likelihood", "AR", "MA", "SCREEN"}, default "linear". Method to use for imputation in series. "mean": use global mean value to fill holes; "previous": propagate last valid observation forward to next valid. "linear": simplest interpolation method; "likelihood":Maximum likelihood estimation based on the normal distribution of speed; "AR": auto regression; "MA": moving average; "SCREEN": speed constraint.
Output Series: Output a single series. The type is the same as the input. This series is the input after repairing.
# Examples
# Fill with linear
When method is "linear" or the default, Screen method is used to impute.
Input series:
+-----------------------------+---------------+
| Time|root.test.d2.s1|
+-----------------------------+---------------+
|2020-01-01T00:00:02.000+08:00| NaN|
|2020-01-01T00:00:03.000+08:00| 101.0|
|2020-01-01T00:00:04.000+08:00| 102.0|
|2020-01-01T00:00:06.000+08:00| 104.0|
|2020-01-01T00:00:08.000+08:00| 126.0|
|2020-01-01T00:00:10.000+08:00| 108.0|
|2020-01-01T00:00:14.000+08:00| NaN|
|2020-01-01T00:00:15.000+08:00| 113.0|
|2020-01-01T00:00:16.000+08:00| 114.0|
|2020-01-01T00:00:18.000+08:00| 116.0|
|2020-01-01T00:00:20.000+08:00| NaN|
|2020-01-01T00:00:22.000+08:00| NaN|
|2020-01-01T00:00:26.000+08:00| 124.0|
|2020-01-01T00:00:28.000+08:00| 126.0|
|2020-01-01T00:00:30.000+08:00| 128.0|
+-----------------------------+---------------+
SQL for query:
select valuefill(s1) from root.test.d2
Output series:
+-----------------------------+-----------------------+
| Time|valuefill(root.test.d2)|
+-----------------------------+-----------------------+
|2020-01-01T00:00:02.000+08:00| NaN|
|2020-01-01T00:00:03.000+08:00| 101.0|
|2020-01-01T00:00:04.000+08:00| 102.0|
|2020-01-01T00:00:06.000+08:00| 104.0|
|2020-01-01T00:00:08.000+08:00| 126.0|
|2020-01-01T00:00:10.000+08:00| 108.0|
|2020-01-01T00:00:14.000+08:00| 108.0|
|2020-01-01T00:00:15.000+08:00| 113.0|
|2020-01-01T00:00:16.000+08:00| 114.0|
|2020-01-01T00:00:18.000+08:00| 116.0|
|2020-01-01T00:00:20.000+08:00| 118.7|
|2020-01-01T00:00:22.000+08:00| 121.3|
|2020-01-01T00:00:26.000+08:00| 124.0|
|2020-01-01T00:00:28.000+08:00| 126.0|
|2020-01-01T00:00:30.000+08:00| 128.0|
+-----------------------------+-----------------------+
# Previous Fill
When method is "previous", previous method is used.
Input series is the same as above, the SQL for query is shown below:
select valuefill(s1,"method"="previous") from root.test.d2
Output series:
+-----------------------------+-------------------------------------------+
| Time|valuefill(root.test.d2,"method"="previous")|
+-----------------------------+-------------------------------------------+
|2020-01-01T00:00:02.000+08:00| NaN|
|2020-01-01T00:00:03.000+08:00| 101.0|
|2020-01-01T00:00:04.000+08:00| 102.0|
|2020-01-01T00:00:06.000+08:00| 104.0|
|2020-01-01T00:00:08.000+08:00| 126.0|
|2020-01-01T00:00:10.000+08:00| 108.0|
|2020-01-01T00:00:14.000+08:00| 110.5|
|2020-01-01T00:00:15.000+08:00| 113.0|
|2020-01-01T00:00:16.000+08:00| 114.0|
|2020-01-01T00:00:18.000+08:00| 116.0|
|2020-01-01T00:00:20.000+08:00| 116.0|
|2020-01-01T00:00:22.000+08:00| 116.0|
|2020-01-01T00:00:26.000+08:00| 124.0|
|2020-01-01T00:00:28.000+08:00| 126.0|
|2020-01-01T00:00:30.000+08:00| 128.0|
+-----------------------------+-------------------------------------------+