SUBROUTINE TVELVC	(nplot, IERROR)
C
C LATEST REVISION   JULY, 1984
C
C PURPOSE		 TO PROVIDE A SIMPLE DEMONSTRATION OF
C			 SUBROUTINES VELVCT AND	EZVEC.
C
C USAGE			 CALL TVELVC (IERROR)
C
C ARGUMENTS
C
C ON OUTPUT		 IERROR
C			   AN INTEGER VARIABLE
C			   =0 IF THERE IS A NORMAL EXIT	FROM THE
C			      ROUTINES VELVCT AND EZVEC
C			   =1 OTHERWISE
C
C I/O			 IF THERE IS A NORMAL EXIT FROM	THE ROUTINES
C			 VELVCT	AND EZVEC THE MESSAGE
C			   VELVCT TEST SUCCESSFUL . . .	SEE PLOTS TO
C			   VERIFY PERFORMANCE
C			 IS PRINTED.
C
C PRECISION		 SINGLE
C
C LANGUAGE		 FORTRAN
C
C HISTORY		 ORIGINALLY WRITTEN NOVEMBER 1976
C
C ALGORITHM		 ROUTINE TVELVC	CALLS ROUTINES EZVEC AND
C			 VELVCT	ONCE.  EACH CALL PRODUCES A PLOT
C			 REPRESENTING A	VECTOR FIELD.  THE VECTOR
C			 FIELD IS OBTAINED FROM	THE FUNCTION
C			   Z(X,Y) = X +	Y + 1./((X-.1)**2+Y**2+.09)
C				    -1./((X+.1)**2+Y**2+.09),
C			 BY USING THE DIRECTION	OF THE Z GRADIENT
C			 VECTORS AND THE LOGARITHM OF THE ABSOLUTE
C			 VALUE OF THE COMPONENTS.
C
C
C
C
      DIMENSION	      U(21,25)	 ,V(21,25)
C
C SPECIFY COORDS FOR PLOT TITLES
C
	DATA IX/94/,IY/1000/
C
C SPECIFY SOME OF THE ARGUMENTS	IN VELVCT CALLING SEQUENCE
C
      DATA FLO/0./,HI/0./,NSET/0/,LENGTH/0/,ISPV/0/,SPV/0./
C
C INITIALIZE ERROR PARAMETER
C
      IERROR = 1
C
C SPECIFY VELOCITY FIELD FUNCTIONS U AND V
C
      M	= 21
      N	= 25
      DO  20 I=1,M
	 X = .1*FLOAT(I-11)
	 DO  10	J=1,N
	    Y =	.1*FLOAT(J-13)
	    DZDX = 1.-2.*(X-.10)/((X-.10)**2+Y**2+.09)**2+
     1		   2.*(X+.10)/((X+.10)**2+Y**2+.09)**2
	    DZDY = 1.-2.*Y/((X-.10)**2+Y**2+.09)**2+
     1		   2.*Y/((X+.10)**2+Y**2+.09)**2
	    UVMAG = ALOG(SQRT(DZDX*DZDX+DZDY*DZDY))
	    UVDIR = ATAN2(DZDY,DZDX)
	    U(I,J) = UVMAG*COS(UVDIR)
	    V(I,J) = UVMAG*SIN(UVDIR)
   10	 CONTINUE
   20 CONTINUE
C
C CALL WTSTR FOR EZVEC PLOT TITLE
C
c +noao: flag used to plot either velvct or ezvec
	if (nplot .eq. 1) then
	CALL GQCNTN(IERR,ICN)
	CALL GSELNT(0)
c       X = PAU2FX(IX)
	x = cpux (ix)
c       Y = PAU2FY(IY)
        y = cpuy (iy)
      CALL WTSTR (X,Y,'DEMONSTRATION PLOT FOR ENTRY EZVEC OF VELVCT',
     1		 2,0,-1)
	CALL GSELNT(ICN)
C
C CALL EZVEC FOR VELOCITY FIELD	PLOT
C
      CALL EZVEC (U,V,M,N)
      endif
c -noao
C
C CALL VELVCT FOR VELOCITY FIELD PLOT
C
c +noao: flag used to plot either velvct or ezvec
      if (nplot .eq. 2) then
      CALL VELVCT (U,M,V,M,M,N,FLO,HI,NSET,LENGTH,ISPV,SPV)
C
C CALL WTSTR FOR VELVCT	PLOT TITLE
C
	CALL GQCNTN(IERR,ICN)
	CALL GSELNT(0)
c       X = PAU2FX(IX)
        x = cpux (ix)
c       Y = PAU2FY(IY)
        y = cpuy (iy)
      CALL WTSTR (X,Y,
     1		 'DEMONSTRATION PLOT FOR ENTRY VELVCT OF VELVCT',2,
     2		 0,-1)
	CALL GSELNT(ICN)
	endif
c -noao
c
c     CALL NEWFM
C
      IERROR = 0
c     WRITE (6,1001)
      RETURN
C
c1001 FORMAT ('	    VELVCT TEST	SUCCESSFUL',24X,
c    1	      'SEE PLOTS TO VERIFY PERFORMANCE')
C
      END