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ui-ngx/src/assets/help/en_US/calculated-field/expression_fn.md
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@ -1,25 +1,31 @@
#### Calculated field TBEL script function
The **calculate()** function is user-defined and receives arguments configured by the user to generate new telemetry data.
It allows you to perform custom calculations using [TBEL{:target="_blank"}](${siteBaseUrl}/docs${docPlatformPrefix}/user-guide/tbel/).
The **calculate()** function is user-defined script that takes values of arguments configured in the calculated field setup and an additional `ctx` object containing all arguments.
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 user-configured arguments and an additional `ctx` object, which provides access to all arguments.
##### Function signature
```javascript
function calculate(arg1, arg2, ...): object | object[]
function calculate(ctx, arg1, arg2, ...): object | object[]
```
The function automatically receives user-defined arguments **(arg1, arg2, ...)** and should return a JSON object.
* the function automatically receives a `ctx` object containing all arguments.
* user-defined arguments `(arg1, arg2, ...)` are passed based on the calculated field configuration.
* the function must return a JSON object (single result) or an array of objects (multiple telemetry entries).
##### Example: Air Density Calculation
This example demonstrates how to calculate air density using altitude and temperature telemetry data.
```javascript
function calculate(altitude, temperature) {
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.value), 5.25588);
var pressure = 101325 * Math.pow((1 - 2.25577e-5 * altitude), 5.25588);
// Air density formula
var airDensity = pressure / (287.05 * temperatureK);
@ -32,7 +38,21 @@ function calculate(altitude, temperature) {
##### Function arguments
The function receives user-configured arguments, which can be of two types:
* `ctx` - context object containing all predefined arguments.
Use `ctx.args.argName` to access arguments.
```javascript
var altitude = ctx.args.altitude.ts;
var temperature = ctx.args.temperature;
```
* `arg1, arg2, ...` - user-defined arguments configured in the calculated field setup. These arguments follow the previously described types:
* if an argument represents the latest telemetry data or attribute, it will be passed as a direct value.
* if an argument is a time series rolling argument, it will be provided as a time series rolling argument described above.
The **calculate()** function receives predefined arguments, which fall into two categories:
* single value arguments - represent the latest telemetry data or attribute.
```json
@ -44,11 +64,11 @@ The function receives user-configured arguments, which can be of two types:
}
```
Use dot notation (`.`) to access argument properties.
Use dot notation (`.`) to access argument properties.
```javascript
var altitudeTimestamp = altitude.ts;
var altitudeValue = altitude.value;
var altitudeTimestamp = ctx.args.altitude.ts;
var altitudeValue = ctx.args.altitude.value;
```
* time series rolling arguments - contain historical data within a defined time window.
@ -57,8 +77,7 @@ The function receives user-configured arguments, which can be of two types:
"temperature": {
"timeWindow": {
"startTs": 1740643762896,
"endTs": 1740644662896,
"limit": 5000
"endTs": 1740644662896
},
"values": [
{ "ts": 1740644355935, "value": 72.32 },
@ -69,8 +88,8 @@ The function receives user-configured arguments, which can be of two types:
}
}
```
Use dot notation (`.`) to access argument properties.
Use dot notation (`.`) to access argument properties.
```javascript
var startOfInterval = temperature.timeWindow.startTs;
@ -81,27 +100,27 @@ The function receives user-configured arguments, which can be of two types:
**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 method has two function signatures:
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. |
| 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. |
| `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:
The following calculations are executed over the provided above arguments:
**Example usage: default (`ignoreNaN = true`)**
@ -139,6 +158,131 @@ var valueCount = temperature.count(false); // Counts all values, including NaN
}
```
Time series rolling arguments can be merged for multi-sensor analysis.
Function Signatures:
* `merge(other, settings)` - merges the current rolling argument with another rolling argument by aligning timestamps and combining values.
Parameters:
* `other` - another time series rolling argument to merge with.
* `settings` (optional) - configuration object, supports:
* `ignoreNaN` (boolean, default true) - controls whether NaN values should be ignored.
* `timeWindow` (object, default {}) - defines a custom time window for filtering merged values.
Returns: an object with time window and values from each provided time series rolling arguments.
* `mergeAll(others, settings)` - merges the current rolling argument with multiple rolling arguments by aligning timestamps and combining values.
Parameters:
* `others` - an array of time series rolling arguments to merge with.
* `settings` (optional) - same as `merge()`.
Returns: an object with timeWindow and aligned values.
```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
}]
}
}
```
**Example 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]
}]
}
}
```
**Example 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 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/).