EquiDepthHistogram (Blazegraph Database Platform 2.1.5 API)

java.lang.Object
- cern.colt.PersistentObject
- - cern.jet.stat.quantile.EquiDepthHistogram

All Implemented Interfaces:

Serializable, Cloneable
```
public class EquiDepthHistogram
extends PersistentObject
```
Read-only equi-depth histogram for selectivity estimation. Assume you have collected statistics over a data set, among them a one-dimensional equi-depth histogram (quantiles). Then an applications or DBMS might want to estimate the selectivity of some range query [from,to], i.e. the percentage of data set elements contained in the query range. This class does not collect equi-depth histograms but only space efficiently stores already produced histograms and provides operations for selectivity estimation. Uses linear interpolation.
This class stores a list l of float values for which holds:
Let v be a list of values (sorted ascending) an equi-depth histogram has been computed over.
Let s=l.length.
Let p=(0, 1/s-1), 2/s-1,..., s-1/s-1=1.0) be a list of the s percentages.
Then for each i=0..s-1: l[i] = e : v.contains(e) && v[0],..., v[p[i]*v.length] <= e.
(In particular: l[0]=min(v)=v[0] and l[s-1]=max(v)=v[s-1].)

Version:: 1.0, 09/24/99
Author:: wolfgang.hoschek@cern.ch
See Also:: Serialized Form

Field Summary

Fields
Modifier and Type Field and Description

protected float[] binBoundaries
- Fields inherited from class cern.colt.PersistentObject
  serialVersionUID

Fields
Modifier and Type	Field and Description
`protected float[]`	`binBoundaries`

Constructor Summary

Constructors
Constructor and Description

EquiDepthHistogram(float[] quantileElements)
Constructs an equi-depth histogram with the given quantile elements.

Constructors
Constructor and Description
`EquiDepthHistogram(float[] quantileElements)` Constructs an equi-depth histogram with the given quantile elements.

Method Summary

Methods
Modifier and Type	Method and Description
`int`	`binOfElement(float element)` Returns the bin index of the given element.
`int`	`bins()` Returns the number of bins.
`float`	`endOfBin(int binIndex)` Returns the end of the range associated with the given bin.
`double`	`percentFromTo(float from, float to)` Returns the percentage of elements in the range (from,to].
`double`	`phi(float element)` Returns how many percent of the elements contained in the receiver are `<= element`.
`int`	`size()` Deprecated. Deprecated. Returns the number of bin boundaries.
`float`	`startOfBin(int binIndex)` Returns the start of the range associated with the given bin.
`static void`	`test(float element)` Not yet commented.

Methods inherited from class cern.colt.PersistentObject
clone

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - binBoundaries
```
protected float[] binBoundaries
```
- Constructor Detail
  - EquiDepthHistogram
```
public EquiDepthHistogram(float[] quantileElements)
```
    Constructs an equi-depth histogram with the given quantile elements. Quantile elements must be sorted ascending and have the form specified in the class documentation.
- Method Detail
  - binOfElement
```
public int binOfElement(float element)
```
    Returns the bin index of the given element. In other words, returns a handle to the range the element falls into.
    
    Parameters:
    element - the element to search for.
    
    Throws:
    
    IllegalArgumentException - if the element is not contained in any bin.
  - bins
```
public int bins()
```
    Returns the number of bins. In other words, returns the number of subdomains partitioning the entire value domain.
  - endOfBin
```
public float endOfBin(int binIndex)
```
    Returns the end of the range associated with the given bin.
    
    Throws:
    
    ArrayIndexOutOfBoundsException - if binIndex < 0 || binIndex >= bins().
  - percentFromTo
```
public double percentFromTo(float from,
                   float to)
```
    Returns the percentage of elements in the range (from,to]. Does linear interpolation.
    
    Parameters:
    from - the start point (exclusive).
    to - the end point (inclusive).
  - phi
```
public double phi(float element)
```
    Returns how many percent of the elements contained in the receiver are <= element. Does linear interpolation.
    
    Parameters:
    the - element to search for.
  - size
```
public int size()
```
    Deprecated. Deprecated. Returns the number of bin boundaries.
  - startOfBin
```
public float startOfBin(int binIndex)
```
    Returns the start of the range associated with the given bin.
    
    Throws:
    
    ArrayIndexOutOfBoundsException - if binIndex < 0 || binIndex >= bins().
  - test
```
public static void test(float element)
```
    Not yet commented.

Class EquiDepthHistogram

Field Summary

Fields inherited from class cern.colt.PersistentObject

Constructor Summary

Method Summary

Methods inherited from class cern.colt.PersistentObject

Methods inherited from class java.lang.Object

Field Detail

binBoundaries

Constructor Detail

EquiDepthHistogram

Method Detail

binOfElement

bins

endOfBin

percentFromTo

phi

size

startOfBin

test