IoTDB-Quality

# Integral

# Usage

This function is used to calculate the integration of time series, which equals to the area under the curve with time as X-axis and values as Y-axis.

Name: INTEGRAL

Input Series: Only support a single input numeric series. The type is INT32 / INT64 / FLOAT / DOUBLE.

Parameters:

  • unit: The unit of time used when computing the integral. The value should be chosen from "1S", "1s", "1m", "1H", "1d"(case-sensitive), and each represents taking one millisecond / second / minute / hour / day as 1.0 while calculating the area and integral.

Output Series: Output a single series. The type is DOUBLE. There is only one data point in the series, whose timestamp is 0 and value is the integration.

Note:

  • The integral value equals to the sum of the areas of right-angled trapezoids consisting of each two adjacent points and the time-axis. Choosing different unit implies different scaling of time axis, thus making it apparent to convert the value among those results with constant coefficient.

  • NaN values in the input series will be ignored. The curve or trapezoids will skip these points and use the next valid point.

# Examples

# Default Parameters

With default parameters, this function will take one second as 1.0.

Input series:

+-----------------------------+---------------+
|                         Time|root.test.d1.s1|
+-----------------------------+---------------+
|2020-01-01T00:00:01.000+08:00|              1|
|2020-01-01T00:00:02.000+08:00|              2|
|2020-01-01T00:00:03.000+08:00|              5|
|2020-01-01T00:00:04.000+08:00|              6|
|2020-01-01T00:00:05.000+08:00|              7|
|2020-01-01T00:00:08.000+08:00|              8|
|2020-01-01T00:00:09.000+08:00|            NaN|
|2020-01-01T00:00:10.000+08:00|             10|
+-----------------------------+---------------+

SQL for query:

select integral(s1) from root.test.d1 where time <= 2020-01-01 00:00:10

Output series:

+-----------------------------+-------------------------+
|                         Time|integral(root.test.d1.s1)|
+-----------------------------+-------------------------+
|1970-01-01T08:00:00.000+08:00|                     57.5|
+-----------------------------+-------------------------+

Calculation expression:

# Specific time unit

With time unit specified as "1m", this function will take one minute as 1.0.

Input series is the same as above, the SQL for query is shown below:

select integral(s1, "unit"="1m") from root.test.d1 where time <= 2020-01-01 00:00:10

Output series:

+-----------------------------+-------------------------+
|                         Time|integral(root.test.d1.s1)|
+-----------------------------+-------------------------+
|1970-01-01T08:00:00.000+08:00|                    0.958|
+-----------------------------+-------------------------+

Calculation expression:

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