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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. |
| Constructor Summary | |
Mean()
Constructs a Mean. |
|
Mean(FirstMoment m1)
Constructs a Mean 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 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 |
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 moment| Method Detail |
public void increment(double d)
StorelessUnivariateStatistic
increment in interface StorelessUnivariateStatisticincrement in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.increment(double)public void clear()
StorelessUnivariateStatistic
clear in interface StorelessUnivariateStatisticclear in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.clear()public double getResult()
StorelessUnivariateStatistic
getResult in interface StorelessUnivariateStatisticgetResult in class AbstractStorelessUnivariateStatisticStorelessUnivariateStatistic.getResult()public long getN()
StorelessUnivariateStatistic
getN in interface StorelessUnivariateStatisticStorelessUnivariateStatistic.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 UnivariateStatisticevaluate in class AbstractStorelessUnivariateStatisticvalues - the input arraybegin - 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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