This is the new *Amazon CloudFormation Template Reference Guide*. Please update your bookmarks and links. For help getting started with CloudFormation, see the [Amazon CloudFormation User Guide](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/Welcome.html).

# AWS::IoTSiteWise::AssetModel Metric
<a name="aws-properties-iotsitewise-assetmodel-metric"></a>

Contains an asset metric property. With metrics, you can calculate aggregate functions, such as an average, maximum, or minimum, as specified through an expression. A metric maps several values to a single value (such as a sum).

The maximum number of dependent/cascading variables used in any one metric calculation is 10. Therefore, a *root* metric can have up to 10 cascading metrics in its computational dependency tree. Additionally, a metric can only have a data type of `DOUBLE` and consume properties with data types of `INTEGER` or `DOUBLE`.

For more information, see [Metrics](https://docs.amazonaws.cn/iot-sitewise/latest/userguide/asset-properties.html#metrics) in the *Amazon IoT SiteWise User Guide*.

## Syntax
<a name="aws-properties-iotsitewise-assetmodel-metric-syntax"></a>

To declare this entity in your Amazon CloudFormation template, use the following syntax:

### JSON
<a name="aws-properties-iotsitewise-assetmodel-metric-syntax.json"></a>

```
{
  "[Expression](#cfn-iotsitewise-assetmodel-metric-expression)" : {{String}},
  "[Variables](#cfn-iotsitewise-assetmodel-metric-variables)" : {{[ ExpressionVariable, ... ]}},
  "[Window](#cfn-iotsitewise-assetmodel-metric-window)" : {{MetricWindow}}
}
```

### YAML
<a name="aws-properties-iotsitewise-assetmodel-metric-syntax.yaml"></a>

```
  [Expression](#cfn-iotsitewise-assetmodel-metric-expression): {{String}}
  [Variables](#cfn-iotsitewise-assetmodel-metric-variables): {{
    - ExpressionVariable}}
  [Window](#cfn-iotsitewise-assetmodel-metric-window): {{
    MetricWindow}}
```

## Properties
<a name="aws-properties-iotsitewise-assetmodel-metric-properties"></a>

`Expression`  <a name="cfn-iotsitewise-assetmodel-metric-expression"></a>
The mathematical expression that defines the metric aggregation function. You can specify up to 10 variables per expression. You can specify up to 10 functions per expression.   
For more information, see [Quotas](https://docs.amazonaws.cn/iot-sitewise/latest/userguide/quotas.html) in the *Amazon IoT SiteWise User Guide*.  
*Required*: Yes  
*Type*: String  
*Update requires*: [No interruption](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)

`Variables`  <a name="cfn-iotsitewise-assetmodel-metric-variables"></a>
The list of variables used in the expression.  
*Required*: Yes  
*Type*: Array of [ExpressionVariable](aws-properties-iotsitewise-assetmodel-expressionvariable.md)  
*Update requires*: [No interruption](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)

`Window`  <a name="cfn-iotsitewise-assetmodel-metric-window"></a>
The window (time interval) over which Amazon IoT SiteWise computes the metric's aggregation expression. Amazon IoT SiteWise computes one data point per `window`.  
*Required*: Yes  
*Type*: [MetricWindow](aws-properties-iotsitewise-assetmodel-metricwindow.md)  
*Update requires*: [No interruption](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)