GNU Octave  4.2.1 A high-level interpreted language, primarily intended for numerical computations, mostly compatible with Matlab
genchi.f
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1  REAL FUNCTION genchi(df)
2 C**********************************************************************
3 C
4 C REAL FUNCTION GENCHI( DF )
5 C Generate random value of CHIsquare variable
6 C
7 C
8 C Function
9 C
10 C
11 C Generates random deviate from the distribution of a chisquare
12 C with DF degrees of freedom random variable.
13 C
14 C
15 C Arguments
16 C
17 C
18 C DF --> Degrees of freedom of the chisquare
19 C (Must be positive)
20 C REAL DF
21 C
22 C
23 C Method
24 C
25 C
26 C Uses relation between chisquare and gamma.
27 C
28 C**********************************************************************
29 C .. Scalar Arguments ..
30  REAL df
31 C ..
32 C .. External Functions ..
33 C REAL gengam
34 C EXTERNAL gengam
35  REAL sgamma
36  EXTERNAL sgamma
37 C ..
38 C .. Executable Statements ..
39  IF (.NOT. (df.LE.0.0)) go to 10
40  WRITE (*,*) 'DF <= 0 in GENCHI - ABORT'
41  WRITE (*,*) 'Value of DF: ',df
42  CALL xstopx('DF <= 0 in GENCHI - ABORT')
43
44 C JJV changed this to call sgamma directly
45 C 10 genchi = 2.0*gengam(1.0,df/2.0)
46  10 genchi = 2.0*sgamma(df/2.0)
47  RETURN
48
49  END
real function genchi(df)
Definition: genchi.f:1
may be zero for pure relative error test tem the relative tolerance must be greater than or equal to