org.jblas.util
Class Permutations

java.lang.Object
  extended by org.jblas.util.Permutations

public class Permutations
extends java.lang.Object


Constructor Summary
Permutations()
           
 
Method Summary
static DoubleMatrix permutationMatrixFromPivotIndices(int size, int[] ipiv)
          Create a permutation matrix from a LAPACK-style 'ipiv' vector.
static int[] randomPermutation(int size)
          Create a random permutation of the numbers 0, ..., size - 1.
static int[] randomSubset(int k, int n)
          Get a random sample of k out of n elements.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

Permutations

public Permutations()
Method Detail

randomPermutation

public static int[] randomPermutation(int size)
Create a random permutation of the numbers 0, ..., size - 1. see Algorithm P, D.E. Knuth: The Art of Computer Programming, Vol. 2, p. 145


randomSubset

public static int[] randomSubset(int k,
                                 int n)
Get a random sample of k out of n elements. See Algorithm S, D. E. Knuth, The Art of Computer Programming, Vol. 2, p.142.


permutationMatrixFromPivotIndices

public static DoubleMatrix permutationMatrixFromPivotIndices(int size,
                                                             int[] ipiv)
Create a permutation matrix from a LAPACK-style 'ipiv' vector.

Parameters:
ipiv - row i was interchanged with row ipiv[i]


written by Mikio L. Braun and Johannes Schaback