StandardDeviation ("The Adobe AEM Quickstart and Web Application.")

java.lang.Object
- org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic
- - org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic
  - - org.apache.commons.math.stat.descriptive.moment.StandardDeviation

All Implemented Interfaces:

java.io.Serializable, StorelessUnivariateStatistic, UnivariateStatistic
```
public class StandardDeviation
extends AbstractStorelessUnivariateStatistic
implements java.io.Serializable
```
Computes the sample standard deviation. The standard deviation is the positive square root of the variance. This implementation wraps a Variance instance. The isBiasCorrected property of the wrapped Variance instance is exposed, so that this class can be used to compute both the "sample standard deviation" (the square root of the bias-corrected "sample variance") or the "population standard deviation" (the square root of the non-bias-corrected "population variance"). See Variance for more information.
Note that this implementation is not synchronized. If multiple threads access an instance of this class concurrently, and at least one of the threads invokes the increment() or clear() method, it must be synchronized externally.

See Also:

Serialized Form

Constructor Summary

Constructors
Constructor and Description
`StandardDeviation()` Constructs a StandardDeviation.
`StandardDeviation(boolean isBiasCorrected)` Contructs a StandardDeviation with the specified value for the `isBiasCorrected` property.
`StandardDeviation(boolean isBiasCorrected, SecondMoment m2)` Contructs a StandardDeviation with the specified value for the `isBiasCorrected` property and the supplied external moment.
`StandardDeviation(SecondMoment m2)` Constructs a StandardDeviation from an external second moment.
`StandardDeviation(StandardDeviation original)` Copy constructor, creates a new `StandardDeviation` identical to the `original`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`clear()` Clears the internal state of the Statistic
`StandardDeviation`	`copy()` Returns a copy of the statistic with the same internal state.
`static void`	`copy(StandardDeviation source, StandardDeviation dest)` Copies source to dest.
`double`	`evaluate(double[] values)` Returns the Standard Deviation of the entries in the input array, or `Double.NaN` if the array is empty.
`double`	`evaluate(double[] values, double mean)` Returns the Standard Deviation of the entries in the input array, using the precomputed mean value.
`double`	`evaluate(double[] values, double mean, int begin, int length)` Returns the Standard Deviation of the entries in the specified portion of the input array, using the precomputed mean value.
`double`	`evaluate(double[] values, int begin, int length)` Returns the Standard Deviation of the entries in the specified portion of the input array, or `Double.NaN` if the designated subarray is empty.
`long`	`getN()` Returns the number of values that have been added.
`double`	`getResult()` Returns the current value of the Statistic.
`void`	`increment(double d)` Updates the internal state of the statistic to reflect the addition of the new value.
`boolean`	`isBiasCorrected()`
`void`	`setBiasCorrected(boolean isBiasCorrected)`

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic
equals, hashCode, incrementAll, incrementAll

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic
evaluate, getData, setData, setData

Methods inherited from class java.lang.Object
getClass, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - StandardDeviation
```
public StandardDeviation()
```
    Constructs a StandardDeviation. Sets the underlying Variance instance's isBiasCorrected property to true.
  - StandardDeviation
```
public StandardDeviation(SecondMoment m2)
```
    Constructs a StandardDeviation from an external second moment.
    
    Parameters:
    
    m2 - the external moment
  - StandardDeviation
```
public StandardDeviation(StandardDeviation original)
```
    Copy constructor, creates a new StandardDeviation identical to the original
    
    Parameters:
    
    original - the StandardDeviation instance to copy
  - StandardDeviation
```
public StandardDeviation(boolean isBiasCorrected)
```
    Contructs a StandardDeviation with the specified value for the isBiasCorrected property. If this property is set to true, the Variance used in computing results will use the bias-corrected, or "sample" formula. See Variance for details.
    
    Parameters:
    
    isBiasCorrected - whether or not the variance computation will use the bias-corrected formula
  - StandardDeviation
```
public StandardDeviation(boolean isBiasCorrected,
                         SecondMoment m2)
```
    Contructs a StandardDeviation with the specified value for the isBiasCorrected property and the supplied external moment. If isBiasCorrected is set to true, the Variance used in computing results will use the bias-corrected, or "sample" formula. See Variance for details.
    
    Parameters:
    
    isBiasCorrected - whether or not the variance computation will use the bias-corrected formula
    
    m2 - the external moment
- Method Detail
  - increment
```
public void increment(double d)
```
    Updates the internal state of the statistic to reflect the addition of the new value.
    
    Specified by:
    
    increment in interface StorelessUnivariateStatistic
    
    Specified by:
    
    increment in class AbstractStorelessUnivariateStatistic
    
    Parameters:
    
    d - the new value.
  - getN
```
public long getN()
```
    Returns the number of values that have been added.
    
    Specified by:
    
    getN in interface StorelessUnivariateStatistic
    
    Returns:
    
    the number of values.
  - getResult
```
public double getResult()
```
    Returns the current value of the Statistic.
    
    Specified by:
    
    getResult in interface StorelessUnivariateStatistic
    
    Specified by:
    
    getResult in class AbstractStorelessUnivariateStatistic
    
    Returns:
    
    value of the statistic, Double.NaN if it has been cleared or just instantiated.
  - clear
```
public void clear()
```
    Clears the internal state of the Statistic
    
    Specified by:
    
    clear in interface StorelessUnivariateStatistic
    
    Specified by:
    
    clear in class AbstractStorelessUnivariateStatistic
  - evaluate
```
public double evaluate(double[] values)
```
    Returns the Standard Deviation of the entries in the input array, or Double.NaN if the array is empty.
    Returns 0 for a single-value (i.e. length = 1) sample.
    
    Throws IllegalArgumentException if the array is null.
    
    Does not change the internal state of the statistic.
    
    Specified by:
    
    evaluate in interface UnivariateStatistic
    
    Overrides:
    
    evaluate in class AbstractStorelessUnivariateStatistic
    
    Parameters:
    
    values - the input array
    
    Returns:
    
    the standard deviation of the values or Double.NaN if length = 0
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is null
    
    See Also:
    
    UnivariateStatistic.evaluate(double[])
  - evaluate
```
public double evaluate(double[] values,
                       int begin,
                       int length)
```
    Returns the Standard Deviation of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.
    Returns 0 for a single-value (i.e. length = 1) sample.
    
    Throws IllegalArgumentException if the array is null.
    
    Does not change the internal state of the statistic.
    
    Specified by:
    
    evaluate in interface UnivariateStatistic
    
    Overrides:
    
    evaluate in class AbstractStorelessUnivariateStatistic
    
    Parameters:
    
    values - the input array
    
    begin - index of the first array element to include
    
    length - the number of elements to include
    
    Returns:
    
    the standard deviation of the values or Double.NaN if length = 0
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is null or the array index parameters are not valid
    
    See Also:
    
    UnivariateStatistic.evaluate(double[], int, int)
  - evaluate
```
public double evaluate(double[] values,
                       double mean,
                       int begin,
                       int length)
```
    Returns the Standard Deviation of the entries in the specified portion of the input array, using the precomputed mean value. Returns Double.NaN if the designated subarray is empty.
    Returns 0 for a single-value (i.e. length = 1) sample.
    
    The formula used assumes that the supplied mean value is the arithmetic mean of the sample data, not a known population parameter. This method is supplied only to save computation when the mean has already been computed.
    
    Throws IllegalArgumentException if the array is null.
    
    Does not change the internal state of the statistic.
    
    Parameters:
    
    values - the input array
    
    mean - the precomputed mean value
    
    begin - index of the first array element to include
    
    length - the number of elements to include
    
    Returns:
    
    the standard deviation of the values or Double.NaN if length = 0
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is null or the array index parameters are not valid
  - evaluate
```
public double evaluate(double[] values,
                       double mean)
```
    Returns the Standard Deviation of the entries in the input array, using the precomputed mean value. Returns Double.NaN if the designated subarray is empty.
    Returns 0 for a single-value (i.e. length = 1) sample.
    
    The formula used assumes that the supplied mean value is the arithmetic mean of the sample data, not a known population parameter. This method is supplied only to save computation when the mean has already been computed.
    
    Throws IllegalArgumentException if the array is null.
    
    Does not change the internal state of the statistic.
    
    Parameters:
    
    values - the input array
    
    mean - the precomputed mean value
    
    Returns:
    
    the standard deviation of the values or Double.NaN if length = 0
    
    Throws:
    
    java.lang.IllegalArgumentException - if the array is null
  - isBiasCorrected
```
public boolean isBiasCorrected()
```
    Returns:
    
    Returns the isBiasCorrected.
  - setBiasCorrected
```
public void setBiasCorrected(boolean isBiasCorrected)
```
    Parameters:
    
    isBiasCorrected - The isBiasCorrected to set.
  - copy
```
public StandardDeviation copy()
```
    Returns a copy of the statistic with the same internal state.
    
    Specified by:
    
    copy in interface StorelessUnivariateStatistic
    
    Specified by:
    
    copy in interface UnivariateStatistic
    
    Specified by:
    
    copy in class AbstractStorelessUnivariateStatistic
    
    Returns:
    
    a copy of the statistic
  - copy
```
public static void copy(StandardDeviation source,
                        StandardDeviation dest)
```
    Copies source to dest.
    Neither source nor dest can be null.
    
    Parameters:
    
    source - StandardDeviation to copy
    
    dest - StandardDeviation to copy to
    
    Throws:
    
    java.lang.NullPointerException - if either source or dest is null

Class StandardDeviation

Constructor Summary

Method Summary

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic

Methods inherited from class java.lang.Object

Constructor Detail

StandardDeviation

StandardDeviation

StandardDeviation

StandardDeviation

StandardDeviation

Method Detail

increment

getN

getResult

clear

evaluate

evaluate

evaluate

evaluate

isBiasCorrected

setBiasCorrected

copy

copy