# "Parametric" Compound metric - HOW TO

#1

Which is the best practice to implement a parametric compound metric?

In the following a quite complete example. Please, give me a feedback if something is wrong. Thanks

Basic Simple Metric:

``````{
"id": "PredictionSimpleMetric_MyType",
"name": "PredictionSimpleMetric",
"srcType": "MyType",
"path": "useCases.(name=='combustionInstability').predictions",
"expression": "avg(avg(normalized.data.value))"
}
``````

Parametric compound metric 1:

``````{
"expression" : "window('AVG', PredictionSimpleMetric, -TGWindow,TGWindow)>TGThreshold",
"variables": [
{
"name": "TGWindow",
"dataType": "int"
},
{
"name": "TGThreshold",
"dataType": "double"
}
]
}
``````

Parametric compound metric 2:

``````{
"expression" : "rollingDiff(window('MIN', AlertRollingMeanTh, -MinDurationOverThreshold, MinDurationOverThreshold))==1",
"variables": [
{
"name": "MinDurationOverThreshold",
"dataType": "int"
}
]
}
``````

Final Compound Metric: Here the compount metric which feeds the parameters with actual values.

``````{
"variables": [
{
"name":"MinDurationOverThreshold",
"dataType": "int",
"value": 1800
},
{
"name":"TGWindow",
"dataType": "int",
"value": 300
},
{
"name":"TGThreshold",
"dataType": "double",
"value": 0.05
}
]
}``````