Package com.inductiveautomation.historian.gateway.query.aggregates

Class VarianceAggregate

java.lang.Object
com.inductiveautomation.historian.gateway.query.aggregates.AbstractAggregationFunction
com.inductiveautomation.historian.gateway.query.aggregates.VarianceAggregate
All Implemented Interfaces:
AggregationFunction
public class VarianceAggregate extends AbstractAggregationFunction
Filename: VarianceAggregate.java Created on Feb 26, 2016 Author: Kathy Applebaum Copyright Inductive Automation 2016 Project: SRGatewayAPI

  • Constructor Details

    • VarianceAggregate

      public VarianceAggregate(AggregationMode mode)
      Mode should be Variance or StdDev

  • Method Details

    • getDataType

      public DataTypeClass getDataType(DataTypeClass columnDataType)
      Description copied from interface: AggregationFunction
      This function returns the type class of the data returned by the function, given the type class of the incoming raw values. For most aggregates this will be equal, but there are some functions that will return a different ype- usually a Float (such as returning a percentage or something).

    • allowValue

      protected boolean allowValue(@Nullable QualifiedValue value, boolean interpolated)
      By default only allows Good quality, non-interpolated.

    • process

      public QualifiedValue[] process(@Nullable QualifiedValue value, boolean interpolatedValue, boolean blockFinished, BlockContext blockContext, QueryContext queryContext)
      Description copied from interface: AggregationFunction
      This function will be called for each value that should be processed, for the entire range of the query. It works in the following way:
      1. For each window, a new BlockContext is created. This object provides some information, but can also be used as a scratch pad for data in the aggregation window.
      2. The function will be called for each value that is actually read from the data source. In this case, interpolatedValue will be false
      3. The function will be called with values at the start of the window and at the end of the window. In these cases, the interpolatedValue boolean will be true (unless raw values just happen to correspond exactly).
      4. The BlockContext contains the previous raw and computed values prior to this block, which can be used for running sums, ongoing calculations, etc.
      5. The return value is only used when blockFinished is true. At the end of the window, the function will be called with an interpolated value for the end time, and blockFinished=true. The function should finalize calculations and return results. (* The function may reuse the return array, and mutate it after returning values)