java.lang.Object
- com.google.common.math.PairedStats

All Implemented Interfaces:

Serializable
```
@Beta
@GwtIncompatible
public final class PairedStats
extends Object
implements Serializable
```
An immutable value object capturing some basic statistics about a collection of paired double values (e.g. points on a plane). Build instances with PairedStatsAccumulator.snapshot().

Since:

20.0

Author:

Pete Gillin

See Also:

Serialized Form

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	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 product-moment 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.

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Method Detail
  - count
```
public long count()
```
    Returns the number of pairs in the dataset.
  - xStats
```
public Stats xStats()
```
    Returns the statistics on the x values alone.
  - yStats
```
public Stats yStats()
```
    Returns the statistics on the y values alone.
  - populationCovariance
```
public double populationCovariance()
```
    Returns the population covariance of the values. The count must be non-zero.
    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.
    Non-finite values
    
    If the dataset contains any non-finite values (Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, or Double.NaN) then the result is Double.NaN.
    
    Throws:
    
    IllegalStateException - if the dataset is empty
  - sampleCovariance
```
public double sampleCovariance()
```
    Returns the sample covariance of the values. The count must be greater than one.
    This is not guaranteed to return zero when the dataset consists of the same pair of values multiple times, due to numerical errors.
    Non-finite values
    
    If the dataset contains any non-finite values (Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, or Double.NaN) then the result is Double.NaN.
    
    Throws:
    
    IllegalStateException - if the dataset is empty or contains a single pair of values
  - pearsonsCorrelationCoefficient
```
public double pearsonsCorrelationCoefficient()
```
    Returns the Pearson's or product-moment correlation coefficient of the values. The count must greater than one, and the x and y values must both have non-zero 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].
    Non-finite values
    
    If the dataset contains any non-finite values (Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, or Double.NaN) then the result is Double.NaN.
    
    Throws:
    
    IllegalStateException - if the dataset is empty or contains a single pair of values, or either the x and y dataset has zero population variance
  - leastSquaresFit
```
public 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. The count must be greater than one, and either the x or y data must have a non-zero 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 root-mean-square 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 root-mean-square 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.
    Non-finite values
    
    If the dataset contains any non-finite values (Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, or Double.NaN) then the result is LinearTransformation.forNaN().
    
    Throws:
    
    IllegalStateException - if the dataset is empty or contains a single pair of values, or both the x and y dataset must have zero population variance
  - equals
```
public boolean equals(@NullableDecl
                      Object obj)
```
    Indicates whether some other object is "equal to" this one.
    The equals method implements an equivalence relation on non-null object references:
    
    It is reflexive: for any non-null reference value x, x.equals(x) should return true.
    It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
    It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
    It is consistent: for any non-null reference values 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.
    For any non-null reference value 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 non-null 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 round-tripping 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.)
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    obj - the reference object with which to compare.
    
    Returns:
    
    true if this object is the same as the obj argument; false otherwise.
    
    See Also:
    
    Object.hashCode(), HashMap
  - hashCode
```
public int hashCode()
```
    Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.
    The general contract of hashCode is:
    
    Whenever it is invoked on the same object more than once during an execution of a Java application, the 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.
    If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
    It is not required that if two objects are unequal according to the 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. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)
    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.
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    a hash code value for this object.
    
    See Also:
    
    Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
  - toString
```
public String toString()
```
    Description copied from class: java.lang.Object
    Returns a string representation of the object. In general, the 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 at-sign 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())
    Overrides:
    
    toString in class Object
    
    Returns:
    
    a string representation of the object.
  - toByteArray
```
public byte[] toByteArray()
```
    Gets a byte array representation of this instance.
    Note: No guarantees are made regarding stability of the representation between versions.
  - fromByteArray
```
public static PairedStats fromByteArray(byte[] byteArray)
```
    Creates a PairedStats instance from the given byte representation which was obtained by toByteArray().
    Note: No guarantees are made regarding stability of the representation between versions.

Class PairedStats

Method Summary

Methods inherited from class java.lang.Object

Method Detail

count

xStats

yStats

populationCovariance

Non-finite values

sampleCovariance

Non-finite values

pearsonsCorrelationCoefficient

Non-finite values

leastSquaresFit

Non-finite values

equals

hashCode

toString

toByteArray

fromByteArray