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Purpose and use of Transformation: | Can be used e.g. to filter out measurement values during periods where the measured system is not in a (quasi) steady state due to changes happening in the system. For example when a pump is switched on/off in a system of pipes, then the pressure in the pipes will fluctuate for some time until reaching an equilibrium value. If data analysis depends only on the equilibrium value, then this transformation can be used to filter out the fluctuating values just after a pump has been switched on/off in the system. |
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Background and Exceptions: | Produces missing output values at times where there is not enough reliable or doubtful data available in the condition and/or expression variables to determine if there is a change or to determine the length of a time window. Any such missing output values are truncated from the start and end of the run period of the transformation, to avoid overwriting data from previous runs with overlapping run periods. |
Detailed description
This transformation copies values from the inputVariable to the outputVariable under certain conditions. The specified conditionVariable is searched for changes during the run period of the transfomation. When the conditionVariable value changes, then a time window is created. This time window starts at the time of the change. The length of the time window (in seconds) is determined by evaluating the specified timeWindowLengthExpression at the time of the change. For each change in the conditionVariable a new time window is created (time windows can overlap). If the specified selectionType is select_inside_time_window, then all inputVariable values that are within at least one time window are copied to the outputVariable and all other inputVariable values are ignored. If selectionType is select_outside_time_window then all inputVariable values that are within at least one time window are ignored and all other inputVariable values are copied to the outputVariable. This can be used e.g. to filter out measurement values during periods where the measured system is not in a (quasi) steady state due to changes happening in the system. Produces missing output values at times where there is not enough reliable or doubtful data available in the condition and/or expression variables to determine if there is a change or to determine the length of a time window. Any such missing output values are truncated from the start and end of the run period of the transformation, to avoid overwriting data from previous runs with overlapping run periods.
variableDefinitions
It is possible to define embedded variables in this transformation. For inputVariable, conditionVariable, outputVariable and in the timeWindowLength expression both embedded variables and variables defined at the start of the transformations configuration file can be used. If an embedded variable and a variable defined at the start of the transformations configuration file have the same variableId, then the embedded variable will be used.
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