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java.lang.Objectorg.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic
org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic
org.apache.commons.math.stat.descriptive.moment.Skewness
Computes the skewness of the available values.
We use the following (unbiased) formula to define skewness:
skewness = [n / (n -1) (n - 2)] sum[(x_i - mean)^3] / std^3
where n is the number of values, mean is the Mean and std is the
StandardDeviation
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.
| Field Summary | |
protected boolean |
incMoment
Determines whether or not this statistic can be incremented or cleared. |
protected ThirdMoment |
moment
Third moment on which this statistic is based |
| Constructor Summary | |
Skewness()
Constructs a Skewness |
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Skewness(ThirdMoment m3)
Constructs a Skewness with an external moment |
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| Method Summary | |
void |
clear()
Clears the internal state of the Statistic |
double |
evaluate(double[] values,
int begin,
int length)
Returns the Skewness of the entries in the specifed portion of the input array. |
long |
getN()
Returns the number of values that have been added. |
double |
getResult()
Returns the value of the statistic based on the values that have been added. |
void |
increment(double d)
Updates the internal state of the statistic to reflect the addition of the new value. |
| Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic |
equals, evaluate, hashCode, incrementAll, incrementAll |
| Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic |
test |
| Methods inherited from class java.lang.Object |
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
protected ThirdMoment moment
protected boolean incMoment
Statistics based on (constructed from) external moments cannot be incremented or cleared.
| Constructor Detail |
public Skewness()
public Skewness(ThirdMoment m3)
m3 - external moment| Method Detail |
public void increment(double d)
StorelessUnivariateStatistic
increment in interface StorelessUnivariateStatisticincrement in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.increment(double)public double getResult()
See Skewness for the definition used in the computation.
getResult in interface StorelessUnivariateStatisticgetResult in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.getResult()public long getN()
StorelessUnivariateStatistic
getN in interface StorelessUnivariateStatisticStorelessUnivariateStatistic.getN()public void clear()
StorelessUnivariateStatistic
clear in interface StorelessUnivariateStatisticclear in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.clear()
public double evaluate(double[] values,
int begin,
int length)
See Skewness for the definition used in the computation.
Throws IllegalArgumentException if the array is null.
evaluate in interface UnivariateStatisticevaluate in class AbstractStorelessUnivariateStatisticvalues - the input arraybegin - the index of the first array element to includelength - the number of elements to include
IllegalArgumentException - if the array is null or the array index
parameters are not validUnivariateStatistic.evaluate(double[], int, int)
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