PLOTXT Subroutine

public subroutine PLOTXT(X, N)

NAME

plotxt(3f) - [M_datapac:LINE_PLOT] generate a line printer run
sequence plot for the terminal (71 characters wide)

SYNOPSIS

   SUBROUTINE PLOTXT(X,N)

    REAL(kind=wp),intent(in) :: X(:)
    INTEGER,intent(in)       :: N

DESCRIPTION

PLOTXT(3f) yields a narrow-width (71-character) plot of x(i) versus i.
Its narrow width makes it appropriate for use on a terminal.

Values in the vertical axis vector (X) which are equal to or in excess
of 10.0**10 will not be plotted.

This convention greatly simplifies the problem of plotting when some
elements in the vector X are 'missing data', or when we purposely
want to ignore certain elements in the vector X for plotting purposes
(that is, we do not want certain elements in X to be plotted). To
cause specific elements in X to be ignored, we replace the elements
beforehand (by, for example, use of the REPLAC(3f) subroutine) by
some large value (like, say, 10.0**10) and they will subsequently be
ignored in the PLOTXT(3f) subroutine.

Note that the storage requirements for this (and the other) terminal
plot subroutiness are very small. This is due to the 'one line at a
time' algorithm employed for the plot.

INPUT ARGUMENTS

X    The vector of (unsorted or sorted) observations to be plotted
     vertically.

N    The integer number of observations in the vector X.

OUTPUT

A narrow-width (71-character) terminal plot of X(I) versus I.
The body of the plot (not counting axis values
and margins) is 25 rows (lines) and 49 columns.

EXAMPLES

Sample program:

program demo_plotxt
use M_datapac, only : plotxt
implicit none
! call plotxt(x,y)
end program demo_plotxt

Results:

AUTHOR

The original DATAPAC library was written by James Filliben of the
Statistical Engineering Division, National Institute of Standards
and Technology.

MAINTAINER

John Urban, 2022.05.31

LICENSE

CC0-1.0

Arguments

Type IntentOptional Attributes Name
real(kind=wp), intent(in) :: X(:)
integer, intent(in) :: N

Source Code

SUBROUTINE PLOTXT(X,N)
REAL(kind=wp),intent(in) :: X(:)
INTEGER,intent(in)       :: N
REAL(kind=wp) :: ai, ailabl, aim1, aimax, aimin, airow, aiwidt, anumcm, anumlm, anumr, anumrm, cutoff, delai, delx, hold
REAL(kind=wp) :: xlable, xlower, xmax, xmin
REAL(kind=wp) :: xupper, xwidth
INTEGER :: i, icol, icolmx, irow, ixdel, numcol, numlab, numr25, numr50, numr75, numrow

CHARACTER(len=4) :: iline
CHARACTER(len=4) :: iaxisc
CHARACTER(len=4) :: sbnam1 , sbnam2
CHARACTER(len=4) :: alph11 , alph12 , alph21 , alph22
CHARACTER(len=4) :: blank , hyphen , alphai , alphax

DIMENSION iline(72) , ailabl(10)

DATA sbnam1 , sbnam2/'PLOT' , 'XT  '/
DATA alph11 , alph12/'FIRS' , 'T   '/
DATA alph21 , alph22/'SECO' , 'ND  '/
DATA blank , hyphen , alphai , alphax/' ' , '-' , 'I' , 'X'/
!
      cutoff = (10.0_wp**10) - 1000.0_wp
!
!     CHECK THE INPUT ARGUMENTS FOR ERRORS
!
      IF ( N<1 ) THEN
         WRITE (G_IO,99010)
         WRITE (G_IO,99011)
         WRITE (G_IO,99012) alph21 , alph22 , sbnam1 , sbnam2
         WRITE (G_IO,99001) N
         99001 FORMAT (' is non-negative (with value = ',I0,')')
         WRITE (G_IO,99010)
         RETURN
      ELSE
         IF ( N==1 ) THEN
            WRITE (G_IO,99010)
            WRITE (G_IO,99011)
            WRITE (G_IO,99012) alph21 , alph22 , sbnam1 , sbnam2
            WRITE (G_IO,99002) N
            99002 FORMAT (' has the value 1')
            WRITE (G_IO,99010)
            RETURN
         ELSE
!
            hold = X(1)
            DO i = 2 , N
               IF ( X(i)/=hold ) GOTO 50
            ENDDO
            WRITE (G_IO,99010)
            WRITE (G_IO,99011)
            WRITE (G_IO,99012) alph11 , alph12 , sbnam1 , sbnam2
            WRITE (G_IO,99003) hold
            99003 FORMAT (' ','has all elements = ',E15.8)
            WRITE (G_IO,99010)
            RETURN
         ENDIF
!
 50      DO i = 1 , N
            IF ( X(i)<cutoff ) GOTO 100
         ENDDO
         WRITE (G_IO,99010)
         WRITE (G_IO,99011)
         WRITE (G_IO,99012) alph11 , alph12 , sbnam1 , sbnam2
         WRITE (G_IO,99004)
         99004 FORMAT (' ','has all elements in excess of the cutoff')
         WRITE (G_IO,99005) cutoff
         99005 FORMAT (' ','value of ',E15.8)
         WRITE (G_IO,99010)
         RETURN
      ENDIF
!
!-----START POINT-----------------------------------------------------
!
!     DEFINE THE NUMBER OF ROWS AND COLUMNS WITHIN THE PLOT--
!     THIS HAS BEEN SET TO 25 ROWS AND 49 COLUMNS.
!
 100  numrow = 25
      numcol = 49
      anumr = numrow
      anumrm = numrow - 1
      anumcm = numcol - 1
      numr25 = (numrow/4) + 1
      numr50 = (numrow/2) + 1
      numr75 = 3*(numrow/4) + 1
      ixdel = (numcol-1)/4
      numlab = 5
      anumlm = numlab - 1
      !
      !     WRITE OUT THE TOP HORIZONTAL AXIS OF THE PLOT, AND SKIP 1 LINE
      !     FOR A MARGIN WITHIN THE PLOT.
      !
      WRITE (G_IO,99006)
      99006 FORMAT (' ')
      WRITE (G_IO,99007)

      99007 FORMAT (' The following is a plot of X(I) (vertically) versus I (horizontally)')
      DO icol = 1 , numcol
         iline(icol) = hyphen
      ENDDO
      DO icol = 1 , numcol , ixdel
         iline(icol) = alphai
      ENDDO
      WRITE (G_IO,99013) (iline(i),i=1,numcol)
      WRITE (G_IO,99014) blank
      !
      !     DETERMINE THE MIN AND MAX VALUES OF X, AND OF I.
      !
      xmin = X(1)
      xmax = X(1)
      aimin = 1
      aimax = N
      DO i = 1 , N
         IF ( X(i)<cutoff ) THEN
            IF ( X(i)<xmin ) xmin = X(i)
            IF ( X(i)>xmax ) xmax = X(i)
         ENDIF
      ENDDO
      delx = xmax - xmin
      delai = aimax - aimin
      xwidth = delx/anumrm
      aiwidt = delai/anumcm
      !
      !     DETERMINE AND WRITE OUT THE PLOT POSITIONS ONE LINE AT A TIME.
      !
      DO irow = 1 , numrow
         DO icol = 1 , numcol
            iline(icol) = blank
         ENDDO
         airow = irow
         xupper = xmax + (1.5_wp-airow)*xwidth
         xlable = xmax + (1.0_wp-airow)*xwidth
         xlower = xmax + (0.5_wp-airow)*xwidth
         IF ( irow==numrow ) xlable = xmin
         DO i = 1 , N
            ai = i
            IF ( X(i)<cutoff ) THEN
               IF ( xlower<=X(i) .AND. X(i)<xupper ) THEN
                  icol = ((ai-aimin)/aiwidt) + 1.5_wp
                  iline(icol) = alphax
               ENDIF
            ENDIF
         ENDDO
         icolmx = 1
         DO icol = 1 , numcol
            IF ( iline(icol)==alphax ) icolmx = icol
         ENDDO
         iaxisc = alphai
         IF ( irow==1 .OR. irow==numrow ) iaxisc = hyphen
         IF ( irow==numr25 .OR. irow==numr50 .OR. irow==numr75 ) iaxisc = hyphen
         WRITE (G_IO,99008) xlable , iaxisc , (iline(icol),icol=1,icolmx)
         99008 FORMAT (' ',E14.7,1X,A1,2X,50A1)
      ENDDO
      !
      !     SKIP 1 LINE FOR A BOTTOM MARGIN WITHIN THE PLOT, WRITE OUT THE
      !     BOTTOM HORIZONTAL AXIS, AND WRITE OUT THE X AXIS LABELS.
      !
      WRITE (G_IO,99014) blank
      DO icol = 1 , numcol
         iline(icol) = hyphen
      ENDDO
      DO icol = 1 , numcol , ixdel
         iline(icol) = alphai
      ENDDO
      WRITE (G_IO,99013) (iline(icol),icol=1,numcol)
      DO i = 1 , numlab
         aim1 = i - 1
         ailabl(i) = aimin + (aim1/anumlm)*delai
      ENDDO
      WRITE (G_IO,99009) (ailabl(i),i=1,numlab)
      99009 FORMAT (' ',9X,5E12.4)

99010 FORMAT (' ','**********************************************************************')
99011 FORMAT (' ','                   FATAL ERROR                    ')
99012 FORMAT (' ','The ',A4,A4,' input argument to the ',A4,A4,' subroutine')
99013 FORMAT (' ',18X,54A1)
99014 FORMAT (' ',15X,A1)

END SUBROUTINE PLOTXT