C DTFG 10
C ..................................................................DTFG 20
C DTFG 30
C SUBROUTINE DQTFG DTFG 40
C DTFG 50
C PURPOSE DTFG 60
C TO COMPUTE THE VECTOR OF INTEGRAL VALUES FOR A GIVEN DTFG 70
C GENERAL TABLE OF ARGUMENT AND FUNCTION VALUES. DTFG 80
C DTFG 90
C USAGE DTFG 100
C CALL DQTFG (X,Y,Z,NDIM) DTFG 110
C DTFG 120
C DESCRIPTION OF PARAMETERS DTFG 130
C X - DOUBLE PRECISION INPUT VECTOR OF ARGUMENT VALUES. DTFG 140
C Y - DOUBLE PRECISION INPUT VECTOR OF FUNCTION VALUES. DTFG 150
C Z - RESULTING DOUBLE PRECISION VECTOR OF INTEGRAL DTFG 160
C VALUES. Z MAY BE IDENTICAL WITH X OR Y. DTFG 170
C NDIM - THE DIMENSION OF VECTORS X,Y,Z. DTFG 180
C DTFG 190
C REMARKS DTFG 200
C NO ACTION IN CASE NDIM LESS THAN 1. DTFG 210
C DTFG 220
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED DTFG 230
C NONE DTFG 240
C DTFG 250
C METHOD DTFG 260
C BEGINNING WITH Z(1)=0, EVALUATION OF VECTOR Z IS DONE BY DTFG 270
C MEANS OF TRAPEZOIDAL RULE (SECOND ORDER FORMULA). DTFG 280
C FOR REFERENCE, SEE DTFG 290
C F.B.HILDEBRAND, INTRODUCTION TO NUMERICAL ANALYSIS, DTFG 300
C MCGRAW-HILL, NEW YORK/TORONTO/LONDON, 1956, PP.75. DTFG 310
C DTFG 320
C ..................................................................DTFG 330
C DTFG 340
SUBROUTINE DQTFG(X,Y,Z,NDIM) DTFG 350
C DTFG 360
C DTFG 370
DIMENSION X(1),Y(1),Z(1) DTFG 380
DOUBLE PRECISION X,Y,Z,SUM1,SUM2 DTFG 390
C DTFG 400
SUM2=0.D0 DTFG 410
IF(NDIM-1)4,3,1 DTFG 420
C DTFG 430
C INTEGRATION LOOP DTFG 440
1 DO 2 I=2,NDIM DTFG 450
SUM1=SUM2 DTFG 460
SUM2=SUM2+.5D0*(X(I)-X(I-1))*(Y(I)+Y(I-1)) DTFG 470
2 Z(I-1)=SUM1 DTFG 480
3 Z(NDIM)=SUM2 DTFG 490
4 RETURN DTFG 500
END DTFG 510