;+ ; NAME: ; SHUFFLE ; ; PURPOSE: ; This function returns the uniformly-shuffled elements of an array. ; ; CATEGORY: ; Math. ; ; CALLING SEQUENCE: ; ; Result = SHUFFLE( A [, Num]) ; ; INPUTS: ; A: Array containing the elements to shuffle (e.g. INDGEN(100)) ; ; OPTIONAL INPUTS: ; Num: Number of shuffled elements to return. Must be < N_ELEMENTS(A)+1 ; ; OPTIONAL INPUT KEYWORD PARAMETERS: ; SEED: Number used to seed the random number generator, RANDOMU. ; ; OUTPUTS: ; Returns the Num shuffled elements of the A array. ; ; OPTIONAL OUTPUT KEYWORD PARAMETERS: ; ; INDICES: Array of indices pointing to the shuffled elements of A. ; ; EXAMPLE: ; Pick 10 unique random integers between the numbers 1..100: ; ; i = INDGEN(100) ; j = SHUFFLE(i,10) ; ; MODIFICATION HISTORY: ; Written by: Han Wen, January 1997. ;- function SHUFFLE, A, Num, INDICES=Indices, SEED=Seed NP = N_PARAMS() N = N_ELEMENTS(A) if (N eq 0) then message, \$ 'Must be called with 1-2 parameters: A [,Num]' if (NP eq 1) then Num = N r = RANDOMU(Seed, N) Indices = SORT(r) return, A(Indices(0:Num-1)) end