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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.Mean
Returns the arithmetic mean of the available values. Uses the definitional formula:
mean = sum(x_i) / n
where n
is the number of observations.
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 boolean |
incMoment
Determines whether or not this statistic can be incremented or cleared. |
protected FirstMoment |
moment
First moment on which this statistic is based. |
(package private) static long |
serialVersionUID
Serializable version identifier |
Constructor Summary | |
Mean()
Constructs a Mean. |
|
Mean(FirstMoment m1)
Constructs a Mean with an External Moment. |
Method Summary | |
void |
clear()
Clears the internal state of the Statistic |
double |
evaluate(double[] values,
int begin,
int length)
Returns the arithmetic mean 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. |
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 |
static final long serialVersionUID
protected FirstMoment moment
protected boolean incMoment
Statistics based on (constructed from) external moments cannot be incremented or cleared.
Constructor Detail |
public Mean()
public Mean(FirstMoment m1)
m1
- the momentMethod Detail |
public void increment(double d)
StorelessUnivariateStatistic
increment
in interface StorelessUnivariateStatistic
increment
in class AbstractStorelessUnivariateStatistic
StorelessUnivariateStatistic.increment(double)
public void clear()
StorelessUnivariateStatistic
clear
in interface StorelessUnivariateStatistic
clear
in class AbstractStorelessUnivariateStatistic
StorelessUnivariateStatistic.clear()
public double getResult()
StorelessUnivariateStatistic
getResult
in interface StorelessUnivariateStatistic
getResult
in class AbstractStorelessUnivariateStatistic
StorelessUnivariateStatistic.getResult()
public long getN()
StorelessUnivariateStatistic
getN
in interface StorelessUnivariateStatistic
StorelessUnivariateStatistic.getN()
public double evaluate(double[] values, int begin, int length)
Double.NaN
if the designated subarray
is empty.
Throws IllegalArgumentException
if the array is null.
See Mean
for details on the computing algorithm.
evaluate
in interface UnivariateStatistic
evaluate
in class AbstractStorelessUnivariateStatistic
values
- the input arraybegin
- index of the first array element to includelength
- the number of elements to include
java.lang.IllegalArgumentException
- if the array is null or the array index
parameters are not validUnivariateStatistic.evaluate(double[], int, int)
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