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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.FirstMoment
public class FirstMoment
Computes the first moment (arithmetic mean). Uses the definitional formula:
mean = sum(x_i) / n
where n is the number of observations.
To limit numeric errors, the value of the statistic is computed using the following recursive updating algorithm:
m = the first valuem = m + (new value - m) / (number of observations)
Returns Double.NaN if the dataset is empty.
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 double |
dev
Deviation of most recently added value from previous first moment. |
protected double |
m1
First moment of values that have been added |
protected long |
n
Count of values that have been added |
protected double |
nDev
Deviation of most recently added value from previous first moment, normalized by previous sample size. |
| Constructor Summary | |
|---|---|
FirstMoment()
Create a FirstMoment instance |
|
FirstMoment(FirstMoment original)
Copy constructor, creates a new FirstMoment identical
to the original |
|
| Method Summary | |
|---|---|
void |
clear()
Clears the internal state of the Statistic |
FirstMoment |
copy()
Returns a copy of the statistic with the same internal state. |
static void |
copy(FirstMoment source,
FirstMoment dest)
Copies source to dest. |
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. |
| Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic |
|---|
equals, evaluate, evaluate, hashCode, incrementAll, incrementAll |
| Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic |
|---|
test, test |
| Methods inherited from class java.lang.Object |
|---|
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
|---|
protected long n
protected double m1
protected double dev
protected double nDev
| Constructor Detail |
|---|
public FirstMoment()
public FirstMoment(FirstMoment original)
FirstMoment identical
to the original
original - the FirstMoment instance to copy| Method Detail |
|---|
public void increment(double d)
increment in interface StorelessUnivariateStatisticincrement in class AbstractStorelessUnivariateStatisticd - the new value.public void clear()
clear in interface StorelessUnivariateStatisticclear in class AbstractStorelessUnivariateStatisticpublic double getResult()
getResult in interface StorelessUnivariateStatisticgetResult in class AbstractStorelessUnivariateStatisticDouble.NaN if it
has been cleared or just instantiated.public long getN()
getN in interface StorelessUnivariateStatisticpublic FirstMoment copy()
copy in interface StorelessUnivariateStatisticcopy in interface UnivariateStatisticcopy in class AbstractStorelessUnivariateStatistic
public static void copy(FirstMoment source,
FirstMoment dest)
Neither source nor dest can be null.
source - FirstMoment to copydest - FirstMoment to copy to
NullPointerException - if either source or dest is null
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