cern.jet.random.sampling
Class RandomSamplingAssistant

java.lang.Object
  cern.colt.PersistentObject
      cern.jet.random.sampling.RandomSamplingAssistant

All Implemented Interfaces:

Cloneable, Serializable

public class RandomSamplingAssistant

extends PersistentObject

Conveniently computes a stable Simple Random Sample Without Replacement (SRSWOR) subsequence of n elements from a given input sequence of N elements; Example: Computing a sublist of n=3 random elements from a list (1,...,50) may yield the sublist (7,13,47). The subsequence is guaranteed to be stable, i.e. elements never change position relative to each other. Each element from the N elements has the same probability to be included in the n chosen elements. This class is a convenience adapter for RandomSampler using blocks.

Version:

1.0, 02/05/99

See Also:

RandomSampler, Serialized Form

RandomSamplingAssistant

public RandomSamplingAssistant(long n,
                               long N,
                               RandomEngine randomGenerator)

Constructs a random sampler that samples n random elements from an input sequence of N elements.

Parameters:

n - the total number of elements to choose (must be >= 0).

N - number of elements to choose from (must be >= n).

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

clone

public Object clone()

Returns a deep copy of the receiver.

Overrides:

clone in class PersistentObject

Returns:

a copy of the receiver.

getRandomGenerator

public RandomEngine getRandomGenerator()

Returns the used random generator.

main

public static void main(String[] args)

Tests random sampling.

sampleArray

public static int[] sampleArray(int n,
                                int[] elements)

Just shows how this class can be used; samples n elements from and int[] array.

sampleNextElement

public boolean sampleNextElement()

Returns whether the next element of the input sequence shall be sampled (picked) or not.

Returns:

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

test

public static void test(long n,
                        long N)

Tests the methods of this class. To do benchmarking, comment the lines printing stuff to the console.

testArraySampling

public static void testArraySampling(int n,
                                     int N)

Tests the methods of this class. To do benchmarking, comment the lines printing stuff to the console.