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## 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

Field Summary

Fields inherited from class cern.colt.PersistentObject
`serialVersionUID`

Constructor Summary
`RandomSamplingAssistant(long n, long N, RandomEngine randomGenerator)` Constructs a random sampler that samples `n` random elements from an input sequence of `N` elements.

Method Summary
`Object` | `clone()` Returns a deep copy of the receiver.
`RandomEngine` | `getRandomGenerator()` Returns the used random generator.
`static void` | `main(String[] args)` Tests random sampling.
`static int[]` | `sampleArray(int n, int[] elements)` Just shows how this class can be used; samples n elements from and int[] array.
`boolean` | `sampleNextElement()` Returns whether the next element of the input sequence shall be sampled (picked) or not.
`static void` | `test(long n, long N)` Tests the methods of this class.
`static void` | `testArraySampling(int n, int N)` Tests the methods of this class.

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

Constructor Detail

### 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.

Method Detail

### 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.

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