cern.jet.random.sampling

Class WeightedRandomSampler

java.lang.Object

cern.colt.PersistentObject

cern.jet.random.sampling.WeightedRandomSampler

All Implemented Interfaces:

Serializable, Cloneable

public class WeightedRandomSampler
extends PersistentObject

Conveniently computes a stable subsequence of elements from a given input sequence; Picks (samples) exactly one random element from successive blocks of weight input elements each. For example, if weight==2 (a block is 2 elements), and the input is 5*2=10 elements long, then picks 5 random elements from the 10 elements such that one element is randomly picked from the first block, one element from the second block, ..., one element from the last block. weight == 1.0 --> all elements are picked (sampled). weight == 10.0 --> Picks one random element from successive blocks of 10 elements each. Etc. The subsequence is guaranteed to be stable, i.e. elements never change position relative to each other.

Version:

1.0, 02/05/99

Author:

wolfgang.hoschek@cern.ch

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Uniform	generator
protected int	nextSkip
protected int	nextTriggerPos
protected int	skip
protected int	weight

Fields inherited from class cern.colt.PersistentObject

serialVersionUID

Constructor Summary

Constructors

Constructor and Description
WeightedRandomSampler() Calls BlockedRandomSampler(1,null).
WeightedRandomSampler(int weight, RandomEngine randomGenerator) Chooses exactly one random element from successive blocks of weight input elements each.

Method Summary

Methods

Modifier and Type	Method and Description
Object	clone() Returns a deep copy of the receiver.
int	getWeight() Not yet commented.
boolean	sampleNextElement() Chooses exactly one random element from successive blocks of weight input elements each.
void	setWeight(int weight) Not yet commented.
static void	test(int weight, int size) Not yet commented.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

skip

protected int skip

nextTriggerPos

protected int nextTriggerPos

nextSkip

protected int nextSkip

weight

protected int weight

generator

protected Uniform generator

Constructor Detail

WeightedRandomSampler

public WeightedRandomSampler()

Calls BlockedRandomSampler(1,null).

WeightedRandomSampler

public WeightedRandomSampler(int weight,
                     RandomEngine randomGenerator)

Chooses exactly one random element from successive blocks of weight input elements each. For example, if weight==2, and the input is 5*2=10 elements long, then chooses 5 random elements from the 10 elements such that one is chosen from the first block, one from the second, ..., one from the last block. weight == 1.0 --> all elements are consumed (sampled). 10.0 --> Consumes one random element from successive blocks of 10 elements each. Etc.

Parameters:

weight - the weight.

randomGenerator - a random number generator. Set this parameter to null to use the default random number generator.

Method Detail

clone

public Object clone()

Returns a deep copy of the receiver.

Overrides:

clone in class PersistentObject

Returns:

a copy of the receiver.

getWeight

public int getWeight()

Not yet commented.

Parameters:

weight - int

sampleNextElement

public boolean sampleNextElement()

Chooses exactly one random element from successive blocks of weight input elements each. For example, if weight==2, and the input is 5*2=10 elements long, then chooses 5 random elements from the 10 elements such that one is chosen from the first block, one from the second, ..., one from the last block.

Returns:

true if the next element shall be sampled (picked), false otherwise.

setWeight

public void setWeight(int weight)

Not yet commented.

Parameters:

weight - int

test

public static void test(int weight,
        int size)

Not yet commented.