*DECK IPPERM SUBROUTINE IPPERM (IX, N, IPERM, IER) C***BEGIN PROLOGUE IPPERM C***PURPOSE Rearrange a given array according to a prescribed C permutation vector. C***LIBRARY SLATEC C***CATEGORY N8 C***TYPE INTEGER (SPPERM-S, DPPERM-D, IPPERM-I, HPPERM-H) C***KEYWORDS APPLICATION OF PERMUTATION TO DATA VECTOR C***AUTHOR McClain, M. A., (NIST) C Rhoads, G. S., (NBS) C***DESCRIPTION C C IPPERM rearranges the data vector IX according to the C permutation IPERM: IX(I) <--- IX(IPERM(I)). IPERM could come C from one of the sorting routines IPSORT, SPSORT, DPSORT or C HPSORT. C C Description of Parameters C IX - input/output -- integer array of values to be rearranged. C N - input -- number of values in integer array IX. C IPERM - input -- permutation vector. C IER - output -- error indicator: C = 0 if no error, C = 1 if N is zero or negative, C = 2 if IPERM is not a valid permutation. C C***REFERENCES (NONE) C***ROUTINES CALLED XERMSG C***REVISION HISTORY (YYMMDD) C 900618 DATE WRITTEN C 920507 Modified by M. McClain to revise prologue text. C***END PROLOGUE IPPERM INTEGER IX(*), N, IPERM(*), I, IER, INDX, INDX0, ITEMP, ISTRT C***FIRST EXECUTABLE STATEMENT IPPERM IER=0 IF(N.LT.1)THEN IER=1 CALL XERMSG ('SLATEC', 'IPPERM', + 'The number of values to be rearranged, N, is not positive.', + IER, 1) RETURN ENDIF C C CHECK WHETHER IPERM IS A VALID PERMUTATION C DO 100 I=1,N INDX=ABS(IPERM(I)) IF((INDX.GE.1).AND.(INDX.LE.N))THEN IF(IPERM(INDX).GT.0)THEN IPERM(INDX)=-IPERM(INDX) GOTO 100 ENDIF ENDIF IER=2 CALL XERMSG ('SLATEC', 'IPPERM', + 'The permutation vector, IPERM, is not valid.', IER, 1) RETURN 100 CONTINUE C C REARRANGE THE VALUES OF IX C C USE THE IPERM VECTOR AS A FLAG. C IF IPERM(I) > 0, THEN THE I-TH VALUE IS IN CORRECT LOCATION C DO 330 ISTRT = 1 , N IF (IPERM(ISTRT) .GT. 0) GOTO 330 INDX = ISTRT INDX0 = INDX ITEMP = IX(ISTRT) 320 CONTINUE IF (IPERM(INDX) .GE. 0) GOTO 325 IX(INDX) = IX(-IPERM(INDX)) INDX0 = INDX IPERM(INDX) = -IPERM(INDX) INDX = IPERM(INDX) GOTO 320 325 CONTINUE IX(INDX0) = ITEMP 330 CONTINUE C RETURN END