RollingStatCalculator (Apache HBase 1.2.12 API)

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java.lang.Object
- org.apache.hadoop.hbase.util.RollingStatCalculator

```
public class RollingStatCalculator
extends Object
```
This class maintains mean and variation for any sequence of input provided to it. It is initialized with number of rolling periods which basically means the number of past inputs whose data will be considered to maintain mean and variation. It will use O(N) memory to maintain these statistics, where N is number of look up periods it was initialized with. If zero is passed during initialization then it will maintain mean and variance from the start. It will use O(1) memory only. But note that since it will maintain mean / variance from the start the statistics may behave like constants and may ignore short trends. All operations are O(1) except the initialization which is O(N).

Field Summary

Fields
Modifier and Type	Field and Description
`private int`	`currentIndexPosition`
`private double`	`currentSqrSum`
`private double`	`currentSum`
`private long[]`	`dataValues`
`private long`	`numberOfDataValues`
`private int`	`rollingPeriod`

Constructor Summary

Constructors
Constructor and Description

RollingStatCalculator(int rollingPeriod)
Creates a RollingStatCalculator with given number of rolling periods.

Method Summary

Methods
Modifier and Type	Method and Description
`private long[]`	`fillWithZeros(int size)`
`double`	`getDeviation()`
`double`	`getMean()`
`void`	`insertDataValue(long data)` Inserts given data value to array of data values to be considered for statistics calculation
`private void`	`removeData(long data)` Update the statistics after removing the given data value

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - currentSum
```
private double currentSum
```
  - currentSqrSum
```
private double currentSqrSum
```
  - numberOfDataValues
```
private long numberOfDataValues
```
  - rollingPeriod
```
private int rollingPeriod
```
  - currentIndexPosition
```
private int currentIndexPosition
```
  - dataValues
```
private long[] dataValues
```
- Constructor Detail
  - RollingStatCalculator
```
public RollingStatCalculator(int rollingPeriod)
```
    Creates a RollingStatCalculator with given number of rolling periods.
    
    Parameters:
    rollingPeriod -
- Method Detail
  - insertDataValue
```
public void insertDataValue(long data)
```
    Inserts given data value to array of data values to be considered for statistics calculation
    
    Parameters:
    data -
  - removeData
```
private void removeData(long data)
```
    Update the statistics after removing the given data value
    
    Parameters:
    data -
  - getMean
```
public double getMean()
```
    Returns:
    mean of the data values that are in the current list of data values
  - getDeviation
```
public double getDeviation()
```
    Returns:
    deviation of the data values that are in the current list of data values
  - fillWithZeros
```
private long[] fillWithZeros(int size)
```
    Parameters:
    size -
    
    Returns:
    an array of given size initialized with zeros

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