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Information

Transformation:

LowPass

Transformation Group:

Filter

Description:

Low pass filter for discrete time series. This transformation calculates the following difference equation.

No Format
 y(t) = b0*x(t) + b1*x(t-1) + ... + bM*x(t-M) + a1*y(t-1) + ... + aN*y(t-N)

Here x is the input, y is the output, t denotes time, b0 to bM are the feedforward coefficients and a1 to aN are the feedback coefficients. When this transformation runs, then it first retrieves the required previous output values from previous runs, if available.

...

Code Block
xml
xml
<variable>
	<variableId>input</variableId>
	<timeSeriesSet>
		<moduleInstanceId>FilterLowPassWithCoefficientSetFunctionsTest</moduleInstanceId>
		<valueType>scalar</valueType>
		<parameterId>H.obs</parameterId>
		<locationId>locationWithAttributes5</locationId>
		<timeSeriesType>external historical</timeSeriesType>
		<timeStep unit="day"/>
		<relativeViewPeriod unit="day" start="10" end="43"/>
		<readWriteMode>editing visible to all future task runs</readWriteMode>
	</timeSeriesSet>
</variable>
<variable>
	<variableId>output</variableId>
	<timeSeriesSet>
		<moduleInstanceId>FilterLowPassWithCoefficientSetFunctionsTest</moduleInstanceId>
		<valueType>scalar</valueType>
		<parameterId>H.m</parameterId>
		<locationId>locationWithAttributes5</locationId>
		<timeSeriesType>external historical</timeSeriesType>
		<timeStep unit="day"/>
		<relativeViewPeriod unit="day" start="10" end="43"/>
		<readWriteMode>add originals</readWriteMode>
	</timeSeriesSet>
</variable>
<transformation id="filter low pass with coefficient set functions test">
	<filter>
		<lowPass>
			<inputVariable>
				<variableId>input</variableId>
			</inputVariable>
			<coefficientSetFunctions>
				<a><at:var at:name="a1" /></<a>@a1@</a>
				<a><at:var at:name="a2" /></<a>@a2@</a>
				<b><at:var at:name="b0" /></<b>@b0@</b>
				<b><at:var at:name="b1" /><<b>@b1@</b>
			</coefficientSetFunctions>
			<outputVariable>
				<variableId>output</variableId>
			</outputVariable>
		</lowPass>
	</filter>
</transformation>