Package cern.jet.stat.quantile
Class EquiDepthHistogram
java.lang.Object
cern.colt.PersistentObject
cern.jet.stat.quantile.EquiDepthHistogram
- All Implemented Interfaces:
Serializable
,Cloneable
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.
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) invalid input: '&'invalid input: '&' 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].)
This class stores a list l of float values for which holds:
- Version:
- 1.0, 09/24/99
- See Also:
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Field Summary
FieldsFields inherited from class cern.colt.PersistentObject
serialVersionUID
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Constructor Summary
ConstructorsConstructorDescriptionEquiDepthHistogram
(float[] quantileElements) Constructs an equi-depth histogram with the given quantile elements. -
Method Summary
Modifier and TypeMethodDescriptionint
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.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
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Field Details
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binBoundaries
protected float[] binBoundaries
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Constructor Details
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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.
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Method Details
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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.
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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().
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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).
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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.
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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().
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test
public static void test(float element) Not yet commented.
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