@Beta @GwtIncompatible public final class PairedStats extends Object implements Serializable
PairedStatsAccumulator.snapshot()
.Modifier and Type  Method and Description 

long 
count()
Returns the number of pairs in the dataset.

boolean 
equals(Object obj)
Indicates whether some other object is "equal to" this one.

static PairedStats 
fromByteArray(byte[] byteArray)
Creates a
PairedStats instance from the given byte representation which was obtained by
toByteArray() . 
int 
hashCode()
Returns a hash code value for the object.

LinearTransformation 
leastSquaresFit()
Returns a linear transformation giving the best fit to the data according to Ordinary Least Squares linear
regression of
y as a function of x . 
double 
pearsonsCorrelationCoefficient()
Returns the Pearson's or
productmoment correlation coefficient of the values.

double 
populationCovariance()
Returns the population covariance of the values.

double 
sampleCovariance()
Returns the sample covariance of the values.

byte[] 
toByteArray()
Gets a byte array representation of this instance.

String 
toString()
Returns a string representation of the object.

Stats 
xStats()
Returns the statistics on the
x values alone. 
Stats 
yStats()
Returns the statistics on the
y values alone. 
public long count()
public double populationCovariance()
This is guaranteed to return zero if the dataset contains a single pair of finite values. It is not guaranteed to return zero when the dataset consists of the same pair of values multiple times, due to numerical errors.
If the dataset contains any nonfinite values (Double.POSITIVE_INFINITY
, Double.NEGATIVE_INFINITY
, or Double.NaN
) then the result is Double.NaN
.
IllegalStateException
 if the dataset is emptypublic double sampleCovariance()
This is not guaranteed to return zero when the dataset consists of the same pair of values multiple times, due to numerical errors.
If the dataset contains any nonfinite values (Double.POSITIVE_INFINITY
, Double.NEGATIVE_INFINITY
, or Double.NaN
) then the result is Double.NaN
.
IllegalStateException
 if the dataset is empty or contains a single pair of valuespublic double pearsonsCorrelationCoefficient()
x
and y
values must both have nonzero population variance (i.e. xStats().populationVariance() > 0.0 && yStats().populationVariance() > 0.0
). The result is not
guaranteed to be exactly +/1 even when the data are perfectly (anti)correlated, due to
numerical errors. However, it is guaranteed to be in the inclusive range [1, +1].
If the dataset contains any nonfinite values (Double.POSITIVE_INFINITY
, Double.NEGATIVE_INFINITY
, or Double.NaN
) then the result is Double.NaN
.
IllegalStateException
 if the dataset is empty or contains a single pair of values, or
either the x
and y
dataset has zero population variancepublic LinearTransformation leastSquaresFit()
y
as a function of x
. The count must be greater than one, and
either the x
or y
data must have a nonzero population variance (i.e. xStats().populationVariance() > 0.0  yStats().populationVariance() > 0.0
). The result is
guaranteed to be horizontal if there is variance in the x
data but not the y
data, and vertical if there is variance in the y
data but not the x
data.
This fit minimizes the rootmeansquare error in y
as a function of x
. This
error is defined as the square root of the mean of the squares of the differences between the
actual y
values of the data and the values predicted by the fit for the x
values (i.e. it is the square root of the mean of the squares of the vertical distances between
the data points and the best fit line). For this fit, this error is a fraction sqrt(1 
R*R)
of the population standard deviation of y
, where R
is the Pearson's
correlation coefficient (as given by pearsonsCorrelationCoefficient()
).
The corresponding rootmeansquare error in x
as a function of y
is a
fraction sqrt(1/(R*R)  1)
of the population standard deviation of x
. This fit
does not normally minimize that error: to do that, you should swap the roles of x
and
y
.
If the dataset contains any nonfinite values (Double.POSITIVE_INFINITY
, Double.NEGATIVE_INFINITY
, or Double.NaN
) then the result is LinearTransformation.forNaN()
.
IllegalStateException
 if the dataset is empty or contains a single pair of values, or
both the x
and y
dataset must have zero population variancepublic boolean equals(@NullableDecl Object obj)
The equals
method implements an equivalence relation
on nonnull object references:
x
, x.equals(x)
should return
true
.
x
and y
, x.equals(y)
should return true
if and only if
y.equals(x)
returns true
.
x
, y
, and z
, if
x.equals(y)
returns true
and
y.equals(z)
returns true
, then
x.equals(z)
should return true
.
x
and y
, multiple invocations of
x.equals(y)
consistently return true
or consistently return false
, provided no
information used in equals
comparisons on the
objects is modified.
x
,
x.equals(null)
should return false
.
The equals
method for class Object
implements
the most discriminating possible equivalence relation on objects;
that is, for any nonnull reference values x
and
y
, this method returns true
if and only
if x
and y
refer to the same object
(x == y
has the value true
).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode
method, which states
that equal objects must have equal hash codes.
Note: This tests exact equality of the calculated statistics, including the floating
point values. Two instances are guaranteed to be considered equal if one is copied from the
other using second = new PairedStatsAccumulator().addAll(first).snapshot()
, if both
were obtained by calling snapshot()
on the same PairedStatsAccumulator
without
adding any values in between the two calls, or if one is obtained from the other after
roundtripping through java serialization. However, floating point rounding errors mean that it
may be false for some instances where the statistics are mathematically equal, including
instances constructed from the same values in a different order... or (in the general case)
even in the same order. (It is guaranteed to return true for instances constructed from the
same values in the same order if strictfp
is in effect, or if the system architecture
guarantees strictfp
like semantics.)
equals
in class Object
obj
 the reference object with which to compare.true
if this object is the same as the obj
argument; false
otherwise.Object.hashCode()
,
HashMap
public int hashCode()
HashMap
.
The general contract of hashCode
is:
hashCode
method
must consistently return the same integer, provided no information
used in equals
comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
equals(Object)
method, then calling the hashCode
method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
method, then calling the hashCode
method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by
class Object
does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
Java™ programming language.)
Note: This hash code is consistent with exact equality of the calculated statistics,
including the floating point values. See the note on equals(java.lang.Object)
for details.
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public String toString()
java.lang.Object
toString
method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the atsign character `@
', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
public byte[] toByteArray()
Note: No guarantees are made regarding stability of the representation between versions.
public static PairedStats fromByteArray(byte[] byteArray)
PairedStats
instance from the given byte representation which was obtained by
toByteArray()
.
Note: No guarantees are made regarding stability of the representation between versions.
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