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REAL FUNCTION genchi(df)
C**********************************************************************
C
C REAL FUNCTION GENCHI( DF )
C Generate random value of CHIsquare variable
C
C
C Function
C
C
C Generates random deviate from the distribution of a chisquare
C with DF degrees of freedom random variable.
C
C
C Arguments
C
C
C DF --> Degrees of freedom of the chisquare
C (Must be positive)
C REAL DF
C
C
C Method
C
C
C Uses relation between chisquare and gamma.
C
C**********************************************************************
C .. Scalar Arguments ..
REAL df
C ..
C .. External Functions ..
C REAL gengam
C EXTERNAL gengam
REAL sgamma
EXTERNAL sgamma
C ..
C .. Executable Statements ..
IF (.NOT. (df.LE.0.0)) GO TO 10
WRITE (*,*) 'DF <= 0 in GENCHI - ABORT'
WRITE (*,*) 'Value of DF: ',df
STOP 'DF <= 0 in GENCHI - ABORT'
C JJV changed this to call sgamma directly
C 10 genchi = 2.0*gengam(1.0,df/2.0)
10 genchi = 2.0*sgamma(df/2.0)
RETURN
END
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