Merge pull request #12809 from irynamatveieva/cf-help-page
CF: help page
This commit is contained in:
Andrew Shvayka
GitHub
commit
fd0e7a543e
@ -1 +1,335 @@
|
||||
<!-- [TODO]: [Calculated Fields] add content -->
|
||||
#### Calculated field TBEL script function
|
||||
|
||||
The **calculate()** function is a user-defined script that allows you to perform custom calculations using [TBEL{:target="_blank"}](${siteBaseUrl}/docs${docPlatformPrefix}/user-guide/tbel/) on telemetry and attribute data.
|
||||
It receives arguments configured in the calculated field setup and an additional `ctx` object, which provides access to all arguments.
|
||||
|
||||
##### Function signature
|
||||
|
||||
```javascript
|
||||
function calculate(ctx, arg1, arg2, ...): object | object[]
|
||||
```
|
||||
|
||||
##### Argument representation in the script
|
||||
|
||||
Before describing how arguments are passed to the function, let's define how different argument types are **represented** inside the script.
|
||||
|
||||
There are two types of arguments that can be used in the function:
|
||||
|
||||
* single value arguments - represent the latest telemetry data or attribute.
|
||||
```json
|
||||
{
|
||||
"altitude": {
|
||||
"ts": 1740644636669,
|
||||
"value": 1034
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
* when accessed via `ctx.args`, they remain objects:
|
||||
|
||||
```javascript
|
||||
var altitudeTimestamp = ctx.args.altitude.ts;
|
||||
var altitudeValue = ctx.args.altitude.value;
|
||||
```
|
||||
|
||||
* when accessed as a **function parameter**, only the value is passed:
|
||||
|
||||
```javascript
|
||||
function calculate(ctx, altitude/*(single value argument)*/, temperature/*(time series rolling argument)*/) {
|
||||
// altitude = 1035
|
||||
}
|
||||
```
|
||||
|
||||
* time series rolling arguments - contain historical data within a defined time window.
|
||||
```json
|
||||
{
|
||||
"temperature": {
|
||||
"timeWindow": {
|
||||
"startTs": 1740643762896,
|
||||
"endTs": 1740644662896
|
||||
},
|
||||
"values": [
|
||||
{ "ts": 1740644355935, "value": 72.32 },
|
||||
{ "ts": 1740644365935, "value": 72.86 },
|
||||
{ "ts": 1740644375935, "value": 73.58 },
|
||||
{ "ts": 1740644385935, "value": "NaN" }
|
||||
]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
* when accessed via `ctx.args`, they remain rolling argument objects:
|
||||
|
||||
```javascript
|
||||
var startOfInterval = temperature.timeWindow.startTs;
|
||||
var firstTimestamp = temperature.values[0].ts;
|
||||
var firstValue = temperature.values[0].value;
|
||||
```
|
||||
|
||||
* when accessed as a **function parameter**, they are passed as rolling arguments, retaining their structure:
|
||||
|
||||
```javascript
|
||||
function calculate(ctx, altitude/*(single value argument)*/, temperature/*(time series rolling argument)*/) {
|
||||
var avgTemp = temperature.mean(); // Use rolling argument functions
|
||||
}
|
||||
```
|
||||
|
||||
**Built-in methods for rolling arguments**
|
||||
|
||||
Time series rolling arguments provide built-in functions for calculations.
|
||||
These functions accept an optional `ignoreNaN` boolean parameter, which controls how NaN values are handled.
|
||||
Each function has two function signatures:
|
||||
|
||||
* **Without parameters:** `method()` → called **without parameters** and defaults to `ignoreNaN = true`, meaning NaN values are ignored.
|
||||
* **With an explicit parameter:** `method(boolean ignoreNaN)` → called with a boolean `ignoreNaN` parameter:
|
||||
* `true` → ignores NaN values (default behavior).
|
||||
* `false` → includes NaN values in calculations.
|
||||
|
||||
| Method | Default Behavior (`ignoreNaN = true`) | Alternative (`ignoreNaN = false`) |
|
||||
|------------|--------------------------------------------------|---------------------------------------------|
|
||||
| `max()` | Returns the highest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
|
||||
| `min()` | Returns the lowest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
|
||||
| `mean()` | Computes the average value, ignoring NaN values. | Returns NaN if any NaN values exist. |
|
||||
| `std()` | Calculates the standard deviation, ignoring NaN. | Returns NaN if any NaN values exist. |
|
||||
| `median()` | Returns the median value, ignoring NaN values. | Returns NaN if any NaN values exist. |
|
||||
| `count()` | Counts only valid (non-NaN) values. | Counts all values, including NaN. |
|
||||
| `last()` | Returns the most recent non-NaN value. | Returns the last value, even if it is NaN. |
|
||||
| `first()` | Returns the oldest non-NaN value. | Returns the first value, even if it is NaN. |
|
||||
| `sum()` | Computes the total sum, ignoring NaN values. | Returns NaN if any NaN values exist. |
|
||||
|
||||
The following calculations are executed over the provided above arguments:
|
||||
|
||||
**Usage: default (`ignoreNaN = true`)**
|
||||
|
||||
```javascript
|
||||
var avgTemp = temperature.mean();
|
||||
var tempMax = temperature.max();
|
||||
var valueCount = temperature.count();
|
||||
```
|
||||
|
||||
**Output:**
|
||||
|
||||
```json
|
||||
{
|
||||
"avgTemp": 72.92,
|
||||
"tempMax": 73.58,
|
||||
"valueCount": 3
|
||||
}
|
||||
```
|
||||
|
||||
**Usage: explicit (`ignoreNaN = false`)**
|
||||
|
||||
```javascript
|
||||
var avgTemp = temperature.mean(false); // Returns NaN if any NaN values exist
|
||||
var tempMax = temperature.max(false); // Returns NaN if any NaN values exist
|
||||
var valueCount = temperature.count(false); // Counts all values, including NaN
|
||||
```
|
||||
|
||||
**Output:**
|
||||
|
||||
```json
|
||||
{
|
||||
"avgTemp": "NaN",
|
||||
"tempMax": "NaN",
|
||||
"valueCount": 4
|
||||
}
|
||||
```
|
||||
|
||||
Time series rolling arguments can be **merged** to align timestamps across multiple datasets.
|
||||
|
||||
| Method | Description | Parameters | Returns |
|
||||
|:-----------------------------|:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:-------------------------------------------------|
|
||||
| `merge(other, settings)` | Merges the current rolling argument with another rolling argument by aligning timestamps and filling missing values with the previous available value. | <ul><li>`other` (another rolling argument)</li><li>`settings` (optional) - configuration object, supports:<ul><br/><li>`ignoreNaN` (boolean, default true) - controls whether NaN values should be ignored.</li><li>`timeWindow` (object, default {}) - defines a custom time window for filtering merged values.</li></ul></li></ul>| Merged object with timeWindow and aligned values. |
|
||||
| `mergeAll(others, settings)` | Merges the current rolling argument with multiple rolling arguments by aligning timestamps and filling missing values with the previous available value. | <ul><li>`others` (array of rolling arguments)</li><li>`settings` (optional) - configuration object, supports:<ul><br/><li>`ignoreNaN` (boolean, default true) - controls whether NaN values should be ignored.</li><li>`timeWindow` (object, default {}) - defines a custom time window for filtering merged values.</li></ul></li></ul>| Merged object with timeWindow and aligned values.|
|
||||
|
||||
**Example arguments:**
|
||||
|
||||
```json
|
||||
{
|
||||
"humidity": {
|
||||
"timeWindow": {
|
||||
"startTs": 1741356332086,
|
||||
"endTs": 1741357232086
|
||||
},
|
||||
"values": [{
|
||||
"ts": 1741356882759,
|
||||
"value": 43
|
||||
}, {
|
||||
"ts": 1741356918779,
|
||||
"value": 46
|
||||
}]
|
||||
},
|
||||
"pressure": {
|
||||
"timeWindow": {
|
||||
"startTs": 1741356332086,
|
||||
"endTs": 1741357232086
|
||||
},
|
||||
"values": [{
|
||||
"ts": 1741357047945,
|
||||
"value": 1023
|
||||
}, {
|
||||
"ts": 1741357056144,
|
||||
"value": 1026
|
||||
}, {
|
||||
"ts": 1741357147391,
|
||||
"value": 1025
|
||||
}]
|
||||
},
|
||||
"temperature": {
|
||||
"timeWindow": {
|
||||
"startTs": 1741356332086,
|
||||
"endTs": 1741357232086
|
||||
},
|
||||
"values": [{
|
||||
"ts": 1741356874943,
|
||||
"value": 76
|
||||
}, {
|
||||
"ts": 1741357063689,
|
||||
"value": 77
|
||||
}]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Usage:**
|
||||
|
||||
```javascript
|
||||
var mergedData = temperature.merge(humidity, { ignoreNaN: false });
|
||||
```
|
||||
|
||||
**Output:**
|
||||
|
||||
```json
|
||||
{
|
||||
"mergedData": {
|
||||
"timeWindow": {
|
||||
"startTs": 1741356332086,
|
||||
"endTs": 1741357232086
|
||||
},
|
||||
"values": [{
|
||||
"ts": 1741356874943,
|
||||
"values": [76.0, "NaN"]
|
||||
}, {
|
||||
"ts": 1741356882759,
|
||||
"values": [76.0, 43.0]
|
||||
}, {
|
||||
"ts": 1741356918779,
|
||||
"values": [76.0, 46.0]
|
||||
}, {
|
||||
"ts": 1741357063689,
|
||||
"values": [77.0, 46.0]
|
||||
}]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
**Usage:**
|
||||
|
||||
```javascript
|
||||
var mergedData = temperature.mergeAll([humidity, pressure], { ignoreNaN: true });
|
||||
```
|
||||
|
||||
**Output:**
|
||||
|
||||
```json
|
||||
{
|
||||
"mergedData": {
|
||||
"timeWindow": {
|
||||
"startTs": 1741356332086,
|
||||
"endTs": 1741357232086
|
||||
},
|
||||
"values": [{
|
||||
"ts": 1741357047945,
|
||||
"values": [76.0, 46.0, 1023.0]
|
||||
}, {
|
||||
"ts": 1741357056144,
|
||||
"values": [76.0, 46.0, 1026.0]
|
||||
}, {
|
||||
"ts": 1741357063689,
|
||||
"values": [77.0, 46.0, 1026.0]
|
||||
}, {
|
||||
"ts": 1741357147391,
|
||||
"values": [77.0, 46.0, 1025.0]
|
||||
}]
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
##### Function arguments
|
||||
|
||||
* `ctx` - context object that contains all provided arguments, in the representations described above.
|
||||
|
||||
Accessing arguments via `ctx`:
|
||||
|
||||
```javascript
|
||||
var altitude = ctx.args.altitude; // single value argument
|
||||
var temperature = ctx.args.temperature; // time series rolling argument
|
||||
```
|
||||
|
||||
* `arg1, arg2, ...` - user-defined arguments configured in the calculated field setup.
|
||||
|
||||
How they are passed depends on their type:
|
||||
|
||||
* **single value arguments** are passed as raw values **(e.g., 22.5, "ON")**.
|
||||
* **time series rolling arguments** are passed as objects (containing multiple values).
|
||||
|
||||
##### Example: Air Density Calculation
|
||||
|
||||
This function calculates air density using `altitude` (single value argument) and `temperature` (time series rolling argument).
|
||||
|
||||
```javascript
|
||||
function calculate(ctx, altitude, temperature) {
|
||||
var avgTemperature = temperature.mean(); // Get average temperature
|
||||
var temperatureK = (avgTemperature - 32) * (5 / 9) + 273.15; // Convert Fahrenheit to Kelvin
|
||||
|
||||
// Estimate air pressure based on altitude
|
||||
var pressure = 101325 * Math.pow((1 - 2.25577e-5 * altitude), 5.25588);
|
||||
|
||||
// Air density formula
|
||||
var airDensity = pressure / (287.05 * temperatureK);
|
||||
|
||||
return {
|
||||
"airDensity": airDensity
|
||||
};
|
||||
}
|
||||
```
|
||||
|
||||
* `altitude` is a single value, passed as number.
|
||||
* `temperature` is a rolling argument, retaining its full structure.
|
||||
|
||||
##### Function return format
|
||||
|
||||
The script should return a JSON object formatted according to the [ThingsBoard Telemetry Upload API](${siteBaseUrl}/docs${docPlatformPrefix}/user-guide/telemetry/#time-series-data-upload-api/).
|
||||
The return value must match one of the supported telemetry upload formats.
|
||||
|
||||
The script must return data in a format compatible with ThingsBoard’s APIs.
|
||||
The correct return format depends on the calculated field output configuration:
|
||||
|
||||
* if latest telemetry is used for output, the function must return data according to the [Telemetry Upload API](${siteBaseUrl}/docs${docPlatformPrefix}/reference/mqtt-api/#attributes-api/).
|
||||
|
||||
* without timestamps
|
||||
```json
|
||||
{
|
||||
"airDensity": 1.06,
|
||||
"someKey": "value"
|
||||
}
|
||||
```
|
||||
* with a timestamp:
|
||||
```json
|
||||
{
|
||||
"ts": 1740644636669,
|
||||
"values": {
|
||||
"airDensity": 1.06,
|
||||
"someKey": "value"
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
* if attributes are used for output, the function must return data according to the [Attributes API](${siteBaseUrl}/docs${docPlatformPrefix}/user-guide/telemetry/#time-series-data-upload-api/).
|
||||
|
||||
```json
|
||||
{
|
||||
"airDensity": 1.06,
|
||||
"someKey": "value"
|
||||
}
|
||||
```
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user