Tuning the documentation of calculated field function
This commit is contained in:
Andrii Shvaika
parent
fd0e7a543e
commit
07d81e58b1
@ -1,151 +1,164 @@
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#### Calculated field TBEL script function
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## Calculated Field TBEL Script Function
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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.
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It receives arguments configured in the calculated field setup and an additional `ctx` object, which provides access to all arguments.
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The **calculate()** function is a user-defined script that enables custom calculations using [TBEL](\${siteBaseUrl}/docs\${docPlatformPrefix}/user-guide/tbel/) on telemetry and attribute data.
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It receives arguments configured in the calculated field setup, along with an additional `ctx` object that provides access to all arguments.
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##### Function signature
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### Function Signature
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```javascript
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function calculate(ctx, arg1, arg2, ...): object | object[]
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function calculate(ctx, arg1, arg2, ...): object | object[]
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```
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##### Argument representation in the script
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### Supported Arguments
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Before describing how arguments are passed to the function, let's define how different argument types are **represented** inside the script.
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There are three types of arguments supported in the calculated field configuration:
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There are two types of arguments that can be used in the function:
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#### Attribute and Latest Telemetry Arguments
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* single value arguments - represent the latest telemetry data or attribute.
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```json
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{
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"altitude": {
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These arguments are single values and may be of type: boolean, int64 (long), double, string, or JSON.
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Attribute and Latest telemetry are single value arguments that may be one of: boolean, int64 (long), double, string and JSON.
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**Example: Convert Temperature from Fahrenheit to Celsius**
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```javascript
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var temperatureC = (temperatureF - 32) / 1.8;
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return {
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"temperatureC": toFixed(temperatureC, 2)
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}
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```
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Alternatively, using `ctx` to access the argument as an object:
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```json
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{
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"temperatureF": {
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"ts": 1740644636669,
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"value": 1034
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"value": 36.6
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}
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}
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```
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}
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```
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* when accessed via `ctx.args`, they remain objects:
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You may notice that the object includes both the `value` of an argument and its timestamp as `ts`.
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Let's modify the function that converts Fahrenheit to Celsius to also return the timestamp information:
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```javascript
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var altitudeTimestamp = ctx.args.altitude.ts;
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var altitudeValue = ctx.args.altitude.value;
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```
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```javascript
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var temperatureC = (temperatureF - 32) / 1.8;
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return {
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"ts": ctx.args.temperatureF.ts,
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"values": { "temperatureC": toFixed(temperatureC, 2) }
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};
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```
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* when accessed as a **function parameter**, only the value is passed:
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#### Time Series Rolling Arguments
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```javascript
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function calculate(ctx, altitude/*(single value argument)*/, temperature/*(time series rolling argument)*/) {
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// altitude = 1035
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}
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```
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These contain time series data within a defined time window. Example format:
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* time series rolling arguments - contain historical data within a defined time window.
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```json
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{
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```json
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{
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"temperature": {
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"timeWindow": {
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"startTs": 1740643762896,
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"endTs": 1740644662896
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},
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"values": [
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{ "ts": 1740644355935, "value": 72.32 },
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{ "ts": 1740644365935, "value": 72.86 },
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{ "ts": 1740644375935, "value": 73.58 },
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{ "ts": 1740644385935, "value": "NaN" }
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{ "ts": 1740644350000, "value": 72.32 },
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{ "ts": 1740644360000, "value": 72.86 },
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{ "ts": 1740644370000, "value": 73.58 },
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{ "ts": 1740644380000, "value": "NaN" }
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]
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}
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}
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```
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The values are always converted to type `double`, and `NaN` is used when conversion fails. One may use `isNaN(double): boolean` function to check that the value is a valid number.
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**Example: Accessing time series rolling argument data**
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```javascript
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var startOfInterval = temperature.timeWindow.startTs;
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var endOfInterval = temperature.timeWindow.endTs;
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var firstItem = temperature.values[0];
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var firstItemTs = firstItem.ts;
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var firstItemValue = firstItem.value;
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var sum = 0.0;
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// iterate through all values and calculate the sum using foreach:
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foreach(t: temperature) {
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if(!isNaN(t.value)) { // check that the value is a valid number;
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sum += t.value;
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}
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```
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}
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// iterate through all values and calculate the sum using for loop:
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sum = 0.0;
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for(var i = 0; i < temperature.values.size; i++) {
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sum += temperature.values[i].value;
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}
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// use built-in function to calculate the sum
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sum = t.sum();
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```
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* when accessed via `ctx.args`, they remain rolling argument objects:
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##### Built-in Methods for Rolling Arguments
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```javascript
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var startOfInterval = temperature.timeWindow.startTs;
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var firstTimestamp = temperature.values[0].ts;
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var firstValue = temperature.values[0].value;
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```
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Time series rolling arguments support built-in functions for calculations. These functions accept an optional `ignoreNaN` boolean parameter.
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* when accessed as a **function parameter**, they are passed as rolling arguments, retaining their structure:
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| Method | Default Behavior (`ignoreNaN = true`) | Alternative (`ignoreNaN = false`) |
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|------------|-----------------------------------------------------|---------------------------------------------|
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| `max()` | Returns the highest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `min()` | Returns the lowest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `mean()` | Computes the average value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `std()` | Calculates the standard deviation, ignoring NaN. | Returns NaN if any NaN values exist. |
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| `median()` | Returns the median value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `count()` | Counts values, ignoring NaN values. | Counts all values, including NaN. |
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| `last()` | Returns the most recent value, skipping NaN values. | Returns the last value, even if it is NaN. |
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| `first()` | Returns the oldest value, skipping NaN values. | Returns the first value, even if it is NaN. |
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| `sum()` | Computes the total sum, ignoring NaN values. | Returns NaN if any NaN values exist. |
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```javascript
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function calculate(ctx, altitude/*(single value argument)*/, temperature/*(time series rolling argument)*/) {
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var avgTemp = temperature.mean(); // Use rolling argument functions
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}
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```
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**Built-in methods for rolling arguments**
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Usage example:
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Time series rolling arguments provide built-in functions for calculations.
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These functions accept an optional `ignoreNaN` boolean parameter, which controls how NaN values are handled.
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Each function has two function signatures:
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```javascript
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var avgTemp = temperature.mean(); // Returns 72.92
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var tempMax = temperature.max(); // Returns 73.58
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var valueCount = temperature.count(); // Returns 3
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* **Without parameters:** `method()` → called **without parameters** and defaults to `ignoreNaN = true`, meaning NaN values are ignored.
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* **With an explicit parameter:** `method(boolean ignoreNaN)` → called with a boolean `ignoreNaN` parameter:
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* `true` → ignores NaN values (default behavior).
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* `false` → includes NaN values in calculations.
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var avgTempNaN = temperature.mean(false); // Returns NaN
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var tempMaxNaN = temperature.max(false); // Returns NaN
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var valueCountNaN = temperature.count(false); // Returns 4
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```
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| Method | Default Behavior (`ignoreNaN = true`) | Alternative (`ignoreNaN = false`) |
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|------------|--------------------------------------------------|---------------------------------------------|
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| `max()` | Returns the highest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `min()` | Returns the lowest value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `mean()` | Computes the average value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `std()` | Calculates the standard deviation, ignoring NaN. | Returns NaN if any NaN values exist. |
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| `median()` | Returns the median value, ignoring NaN values. | Returns NaN if any NaN values exist. |
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| `count()` | Counts only valid (non-NaN) values. | Counts all values, including NaN. |
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| `last()` | Returns the most recent non-NaN value. | Returns the last value, even if it is NaN. |
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| `first()` | Returns the oldest non-NaN value. | Returns the first value, even if it is NaN. |
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| `sum()` | Computes the total sum, ignoring NaN values. | Returns NaN if any NaN values exist. |
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This function calculates air density using `altitude` (single value) and `temperature` (time series rolling argument).
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The following calculations are executed over the provided above arguments:
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```javascript
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function calculate(ctx, altitude, temperature) {
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var avgTemperature = temperature.mean(); // Get average temperature
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var temperatureK = (avgTemperature - 32) * (5 / 9) + 273.15; // Convert Fahrenheit to Kelvin
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**Usage: default (`ignoreNaN = true`)**
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// Estimate air pressure based on altitude
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var pressure = 101325 * Math.pow((1 - 2.25577e-5 * altitude), 5.25588);
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```javascript
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var avgTemp = temperature.mean();
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var tempMax = temperature.max();
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var valueCount = temperature.count();
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```
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// Air density formula
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var airDensity = pressure / (287.05 * temperatureK);
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**Output:**
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return {
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"airDensity": airDensity
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};
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}
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```
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```json
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{
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"avgTemp": 72.92,
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"tempMax": 73.58,
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"valueCount": 3
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}
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```
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##### Merging Time Series Arguments
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**Usage: explicit (`ignoreNaN = false`)**
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Time series rolling arguments can be **merged** to align timestamps across multiple datasets.
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```javascript
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var avgTemp = temperature.mean(false); // Returns NaN if any NaN values exist
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var tempMax = temperature.max(false); // Returns NaN if any NaN values exist
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var valueCount = temperature.count(false); // Counts all values, including NaN
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```
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| Method | Description | Parameters | Returns |
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|:-----------------------------|:--------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:-------------------------------------------------|
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| `merge(other, settings)` | Merges with another rolling argument. Aligns 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. |
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| `mergeAll(others, settings)` | Merges with multiple rolling arguments. Aligns 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.|
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**Output:**
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Assuming the following arguments and their values:
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```json
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{
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"avgTemp": "NaN",
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"tempMax": "NaN",
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"valueCount": 4
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}
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```
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Time series rolling arguments can be **merged** to align timestamps across multiple datasets.
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| Method | Description | Parameters | Returns |
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|:-----------------------------|:-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|:-------------------------------------------------|
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| `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. |
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| `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.|
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**Example arguments:**
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```json
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{
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```json
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{
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"humidity": {
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"timeWindow": {
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"startTs": 1741356332086,
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@ -188,19 +201,19 @@ There are two types of arguments that can be used in the function:
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"value": 77
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}]
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}
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}
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```
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}
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```
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**Usage:**
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**Usage:**
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```javascript
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var mergedData = temperature.merge(humidity, { ignoreNaN: false });
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```
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```javascript
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var mergedData = temperature.merge(humidity, { ignoreNaN: false });
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```
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**Output:**
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**Output:**
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```json
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{
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```json
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{
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"mergedData": {
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"timeWindow": {
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"startTs": 1741356332086,
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@ -220,19 +233,19 @@ There are two types of arguments that can be used in the function:
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"values": [77.0, 46.0]
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}]
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}
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}
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```
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}
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```
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**Usage:**
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**Usage:**
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```javascript
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var mergedData = temperature.mergeAll([humidity, pressure], { ignoreNaN: true });
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```
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```javascript
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var mergedData = temperature.mergeAll([humidity, pressure], { ignoreNaN: true });
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```
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**Output:**
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**Output:**
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```json
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{
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```json
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{
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"mergedData": {
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"timeWindow": {
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"startTs": 1741356332086,
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@ -252,84 +265,136 @@ There are two types of arguments that can be used in the function:
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"values": [77.0, 46.0, 1025.0]
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}]
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}
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}
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```
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##### Function arguments
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* `ctx` - context object that contains all provided arguments, in the representations described above.
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Accessing arguments via `ctx`:
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```javascript
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var altitude = ctx.args.altitude; // single value argument
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var temperature = ctx.args.temperature; // time series rolling argument
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```
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* `arg1, arg2, ...` - user-defined arguments configured in the calculated field setup.
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How they are passed depends on their type:
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* **single value arguments** are passed as raw values **(e.g., 22.5, "ON")**.
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* **time series rolling arguments** are passed as objects (containing multiple values).
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##### Example: Air Density Calculation
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This function calculates air density using `altitude` (single value argument) and `temperature` (time series rolling argument).
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```javascript
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function calculate(ctx, altitude, temperature) {
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var avgTemperature = temperature.mean(); // Get average temperature
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var temperatureK = (avgTemperature - 32) * (5 / 9) + 273.15; // Convert Fahrenheit to Kelvin
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// Estimate air pressure based on altitude
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var pressure = 101325 * Math.pow((1 - 2.25577e-5 * altitude), 5.25588);
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// Air density formula
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var airDensity = pressure / (287.05 * temperatureK);
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return {
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"airDensity": airDensity
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};
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}
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```
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* `altitude` is a single value, passed as number.
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* `temperature` is a rolling argument, retaining its full structure.
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**Example: Freezer temperature analysis**
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##### Function return format
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This function merges `temperature` data with the fridge's `defrost` status. It then analyzes the merged data to identify instances where the fridge is not in defrost mode, yet the internal air temperature is too high ( > -5° C).
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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/).
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The return value must match one of the supported telemetry upload formats.
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```javascript
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function calculate(ctx, temperature, defrost) {
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var merged = temperature.merge(defrost);
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var result = [];
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The script must return data in a format compatible with ThingsBoard’s APIs.
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The correct return format depends on the calculated field output configuration:
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* 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/).
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* without timestamps
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```json
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{
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"airDensity": 1.06,
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"someKey": "value"
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foreach(item: merged) {
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if (item.v1 > -5.0 && item.v2 == 0) {
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result.add({
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ts: item.ts,
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values: {
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issue: {
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temperature: item.v1,
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defrostState: false
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}
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```
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* with a timestamp:
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```json
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{
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}
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});
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}
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}
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return result;
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}
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```
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The result is a list of issues that may be used to configure alarm rules:
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```json
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[{
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"ts": 1741613833843,
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"values": {
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"issue": {
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"temperature": -3.12,
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"defrostState": false
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}
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}
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}, {
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"ts": 1741613923848,
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"values": {
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"issue": {
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"temperature": -4.16,
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"defrostState": false
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}
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}
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}]
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```
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### Function return format
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The return format depends on the output type configured in the calculated field settings (default: **Time Series**).
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##### Time Series Output
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The function must return a JSON object or array with or without a timestamp.
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Examples below return 5 data points: airDensity (double), humidity (integer), hvacEnabled (boolean), hvacState (string) and configuration (JSON):
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Without timestamp:
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```json
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{
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"airDensity": 1.06,
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"humidity": 70,
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"hvacEnabled": true,
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"hvacState": "IDLE",
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"configuration": {
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"someNumber": 42,
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"someArray": [1,2,3],
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"someNestedObject": {"key": "value"}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
With timestamp:
|
||||
|
||||
```json
|
||||
{
|
||||
"ts": 1740644636669,
|
||||
"values": {
|
||||
"airDensity": 1.06,
|
||||
"someKey": "value"
|
||||
"humidity": 70,
|
||||
"hvacEnabled": true,
|
||||
"hvacState": "IDLE",
|
||||
"configuration": {
|
||||
"someNumber": 42,
|
||||
"someArray": [1,2,3],
|
||||
"someNestedObject": {"key": "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/).
|
||||
Array containing multiple timestamps and different values of the `airDensity` :
|
||||
|
||||
```json
|
||||
```json
|
||||
[
|
||||
{
|
||||
"airDensity": 1.06,
|
||||
"someKey": "value"
|
||||
"ts": 1740644636669,
|
||||
"values": {
|
||||
"airDensity": 1.06
|
||||
}
|
||||
```
|
||||
},
|
||||
{
|
||||
"ts": 1740644636670,
|
||||
"values": {
|
||||
"airDensity": 1.07
|
||||
}
|
||||
}
|
||||
]
|
||||
```
|
||||
|
||||
##### Attribute Output
|
||||
|
||||
The function must return a JSON object **without timestamp** information.
|
||||
Example below return 5 data points: airDensity (double), humidity (integer), hvacEnabled (boolean), hvacState (string) and configuration (JSON):
|
||||
|
||||
```json
|
||||
{
|
||||
"airDensity": 1.06,
|
||||
"humidity": 70,
|
||||
"hvacEnabled": true,
|
||||
"hvacState": "IDLE",
|
||||
"configuration": {
|
||||
"someNumber": 42,
|
||||
"someArray": [1,2,3],
|
||||
"someNestedObject": {"key": "value"}
|
||||
}
|
||||
}
|
||||
```
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user