public class Kurtosis extends AbstractStorelessUnivariateStatistic implements Serializable
We use the following (unbiased) formula to define kurtosis:
kurtosis = { [n(n+1) / (n -1)(n - 2)(n-3)] sum[(x_i - mean)^4] / std^4 } - [3(n-1)^2 / (n-2)(n-3)]
where n is the number of values, mean is the Mean and std is the
StandardDeviation
Note that this statistic is undefined for n < 4. Double.Nan
is returned when there is not sufficient data to compute the statistic.
Note that Double.NaN may also be returned if the input includes NaN
and / or infinite values.
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.
| Modifier and Type | Field and Description |
|---|---|
protected boolean |
incMoment
Determines whether or not this statistic can be incremented or cleared.
|
protected org.apache.commons.math4.stat.descriptive.moment.FourthMoment |
moment
Fourth Moment on which this statistic is based
|
| Constructor and Description |
|---|
Kurtosis()
Construct a Kurtosis.
|
Kurtosis(org.apache.commons.math4.stat.descriptive.moment.FourthMoment m4)
Construct a Kurtosis from an external moment.
|
Kurtosis(Kurtosis original)
Copy constructor, creates a new
Kurtosis identical
to the original. |
| Modifier and Type | Method and Description |
|---|---|
void |
clear()
Clears the internal state of the Statistic
|
Kurtosis |
copy()
Returns a copy of the statistic with the same internal state.
|
static void |
copy(Kurtosis source,
Kurtosis dest)
Copies source to dest.
|
double |
evaluate(double[] values,
int begin,
int length)
Returns the kurtosis of the entries in the specified portion of the
input array.
|
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.
|
equals, evaluate, hashCode, incrementAll, incrementAllprotected org.apache.commons.math4.stat.descriptive.moment.FourthMoment moment
protected boolean incMoment
Statistics based on (constructed from) external moments cannot be incremented or cleared.
public Kurtosis()
public Kurtosis(org.apache.commons.math4.stat.descriptive.moment.FourthMoment m4)
m4 - external Momentpublic Kurtosis(Kurtosis original) throws NullArgumentException
Kurtosis identical
to the original.original - the Kurtosis instance to copyNullArgumentException - if original is nullpublic void increment(double d)
Note that when Kurtosis(FourthMoment) is used to
create a Variance, this method does nothing. In that case, the
FourthMoment should be incremented directly.
increment in interface StorelessUnivariateStatisticincrement in class AbstractStorelessUnivariateStatisticd - the new value.public double getResult()
getResult in interface StorelessUnivariateStatisticgetResult in class AbstractStorelessUnivariateStatisticDouble.NaN if it
has been cleared or just instantiated.public void clear()
clear in interface StorelessUnivariateStatisticclear in class AbstractStorelessUnivariateStatisticpublic long getN()
getN in interface StorelessUnivariateStatisticpublic double evaluate(double[] values,
int begin,
int length)
throws MathIllegalArgumentException
See Kurtosis for details on the computing algorithm.
Throws IllegalArgumentException if the array is null.
evaluate in interface UnivariateStatisticevaluate in interface MathArrays.Functionevaluate in class AbstractStorelessUnivariateStatisticvalues - the input arraybegin - index of the first array element to includelength - the number of elements to includeMathIllegalArgumentException - if the input array is null or the array
index parameters are not validUnivariateStatistic.evaluate(double[], int, int)public Kurtosis copy()
copy in interface StorelessUnivariateStatisticcopy in interface UnivariateStatisticcopy in class AbstractStorelessUnivariateStatisticpublic static void copy(Kurtosis source, Kurtosis dest) throws NullArgumentException
Neither source nor dest can be null.
source - Kurtosis to copydest - Kurtosis to copy toNullArgumentException - if either source or dest is nullCopyright © 2003–2015 The Apache Software Foundation. All rights reserved.