VarSAggregator (Apache Derby V10.14 Internals)

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Summary:
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Field |
Constr |
Method

Detail:
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Constr |
Method

java.lang.Object
- org.apache.derby.impl.sql.execute.VarPAggregator<V>
- - org.apache.derby.impl.sql.execute.VarSAggregator<V>

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, Aggregator<V,java.lang.Double,VarPAggregator<V>>

Direct Known Subclasses:

StdDevSAggregator
```
public class VarSAggregator<V extends java.lang.Number>
extends VarPAggregator<V>
```
This class implements the SQL Standard VAR_SAMP() aggregator, computing the variance over a sample. It uses the IBM formula described here:
```
 [ sum(x_i²) - sum(x_i)²/n ]/(n-1)
 
 where
 
 n is the number of items in the population
 x₁ ... x_n are the items in the population
 
```
See Also:

Serialized Form

- Nested Class Summary
  - Nested classes/interfaces inherited from class org.apache.derby.impl.sql.execute.VarPAggregator
    VarPAggregator.Sums
- Field Summary
  
  Fields
  Modifier and Type Field Description
  
  private static long serialVersionUID
  - Fields inherited from class org.apache.derby.impl.sql.execute.VarPAggregator
    count, sums
- Constructor Summary
  
  Constructors
  Constructor Description
  
  VarSAggregator()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  protected java.lang.Double computeVar()
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  - Methods inherited from class org.apache.derby.impl.sql.execute.VarPAggregator
    accumulate, init, merge, readExternal, terminate, writeExternal

- Field Detail
  - serialVersionUID
```
private static final long serialVersionUID
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - VarSAggregator
```
public VarSAggregator()
```
- Method Detail
  - computeVar
```
protected java.lang.Double computeVar()
```
    Overrides:
    
    computeVar in class VarPAggregator<V extends java.lang.Number>

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Built on Wed 2018-05-16 16:01:03+0000, from revision ???

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Apache Derby V10.14 Internals - Copyright © 2004,2018 The Apache Software Foundation. All Rights Reserved.