[u/mrichter/AliRoot.git] / MINICERN / mathlib / gen / g / studis.F

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1996/04/01 15:02:42  mclareni
* Mathlib gen
*
*
#include "gen/pilot.h"
      FUNCTION STUDIS(T,N)
C    THIS ROUTINE COMPUTES THE DISTRIBUTION FUNCTION OF THE
C    STUDENT DISTRIBUTION WITH N DEGREES OF FREEDOM.
C    T=VALUE OF THE INDEPENDENT VARIABLE,
C    N=INTEGER GREATER THAN ZERO.
C    THE ROUTINE WAS WRITTEN  BY B.E. COOPER,APPLIED STATISTICS,
C     17(1968)189-190
C    ALGORITHM AS3. THE METHOD WHICH IS THEORETICALLY EXACT WAS GIVEN BY
C    D.B. OWEN,BIOMETRIKA,52(1965),437-446.
C    AT LEAST 9 DECIMAL PLACES ARE CORRECT.
      DATA G1/0.31830988618379/
      IF(N-1) 1,2,3
    2 STUDIS=0.5+G1*ATAN(T)
      RETURN
    3 FN=N
      A=T/SQRT(FN)
      B=FN/(FN+T*T)
      S=1.
      N2=N-2
      N3=MOD(N,2)
      IF(N2 .LT. 2) GO TO 4
      C=1.
      K=2+N3
      FK=K
      DO 5 I=K,N2,2
           C=C*B*(FK-1.)/FK
           S=S+C
    5      FK=FK+2.
    4 IF(N3 .NE. 0) GO TO 6
      STUDIS=0.5+0.5*A*SQRT(B)*S
      RETURN
    6 STUDIS=0.5+(A*B*S+ATAN(A))*G1
      RETURN
    1 WRITE(6,7) N
      STOP
    7 FORMAT(/10X,'DEGREE OF FREEDOM N=',I5,' IN STUDIS ILLEGAL'/)
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1996/04/01 15:02:42 mclareni
	6	* Mathlib gen
	7	*
	8	*
	9	#include "gen/pilot.h"
	10	FUNCTION STUDIS(T,N)
	11	C THIS ROUTINE COMPUTES THE DISTRIBUTION FUNCTION OF THE
	12	C STUDENT DISTRIBUTION WITH N DEGREES OF FREEDOM.
	13	C T=VALUE OF THE INDEPENDENT VARIABLE,
	14	C N=INTEGER GREATER THAN ZERO.
	15	C THE ROUTINE WAS WRITTEN BY B.E. COOPER,APPLIED STATISTICS,
	16	C 17(1968)189-190
	17	C ALGORITHM AS3. THE METHOD WHICH IS THEORETICALLY EXACT WAS GIVEN BY
	18	C D.B. OWEN,BIOMETRIKA,52(1965),437-446.
	19	C AT LEAST 9 DECIMAL PLACES ARE CORRECT.
	20	DATA G1/0.31830988618379/
	21	IF(N-1) 1,2,3
	22	2 STUDIS=0.5+G1*ATAN(T)
	23	RETURN
	24	3 FN=N
	25	A=T/SQRT(FN)
	26	B=FN/(FN+T*T)
	27	S=1.
	28	N2=N-2
	29	N3=MOD(N,2)
	30	IF(N2 .LT. 2) GO TO 4
	31	C=1.
	32	K=2+N3
	33	FK=K
	34	DO 5 I=K,N2,2
	35	C=CB(FK-1.)/FK
	36	S=S+C
	37	5 FK=FK+2.
	38	4 IF(N3 .NE. 0) GO TO 6
	39	STUDIS=0.5+0.5ASQRT(B)*S
	40	RETURN
	41	6 STUDIS=0.5+(ABS+ATAN(A))*G1
	42	RETURN
	43	1 WRITE(6,7) N
	44	STOP
	45	7 FORMAT(/10X,'DEGREE OF FREEDOM N=',I5,' IN STUDIS ILLEGAL'/)
	46	END