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java.lang.Objectorg.apache.openejb.math.stat.descriptive.AbstractUnivariateStatistic
org.apache.openejb.math.stat.descriptive.AbstractStorelessUnivariateStatistic
org.apache.openejb.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.openejb.math.stat.descriptive.AbstractStorelessUnivariateStatistic |
---|
equals, evaluate, evaluate, hashCode, incrementAll, incrementAll |
Methods inherited from class org.apache.openejb.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 |
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public FirstMoment()
public FirstMoment(FirstMoment original)
FirstMoment
identical
to the original
original
- the FirstMoment
instance to copyMethod Detail |
---|
public void increment(double d)
increment
in interface StorelessUnivariateStatistic
increment
in class AbstractStorelessUnivariateStatistic
d
- the new value.public void clear()
clear
in interface StorelessUnivariateStatistic
clear
in class AbstractStorelessUnivariateStatistic
public double getResult()
getResult
in interface StorelessUnivariateStatistic
getResult
in class AbstractStorelessUnivariateStatistic
Double.NaN
if it
has been cleared or just instantiated.public long getN()
getN
in interface StorelessUnivariateStatistic
public FirstMoment copy()
copy
in interface StorelessUnivariateStatistic
copy
in interface UnivariateStatistic
copy
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
java.lang.NullPointerException
- if either source or dest is null
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