Name:         PGBOX

Purpose:      draw labeled frame around viewport

Category:     GRAPHICS

File:         pgplot.src

Author:       T.J. Pearson

Use:          see description below.

Description:

            SUBROUTINE PGBOX (XOPT, XTICK, NXSUB, YOPT, YTICK, NYSUB)
            CHARACTER*(*) XOPT, YOPT
            REAL XTICK, YTICK
            INTEGER NXSUB, NYSUB
      
       Annotate the viewport with frame, axes, numeric labels, etc.
       PGBOX is called by on the user's behalf by PGENV, but may also be
       called explicitly.
      
       Arguments:
        XOPT   (input)  : string of options for X (horizontal) axis of
                          plot. Options are single letters, and may be in
                          any order (see below).
        XTICK  (input)  : world coordinate interval between major tick marks
                          on X axis. If XTICK=0.0, the interval is chosen by
                          PGBOX, so that there will be at least 3 major tick
                          marks along the axis.
        NXSUB  (input)  : the number of subintervals to divide the major
                          coordinate interval into. If XTICK=0.0 or NXSUB=0,
                          the number is chosen by PGBOX.
        YOPT   (input)  : string of options for Y (vertical) axis of plot.
                          Coding is the same as for XOPT.
        YTICK  (input)  : like XTICK for the Y axis.
        NYSUB  (input)  : like NXSUB for the Y axis.
      
       Options (for parameters XOPT and YOPT):
        A : draw Axis (X axis is horizontal line Y=0, Y axis is vertical
            line X=0).
        B : draw bottom (X) or left (Y) edge of frame.
        C : draw top (X) or right (Y) edge of frame.
        G : draw Grid of vertical (X) or horizontal (Y) lines.
        I : Invert the tick marks; ie draw them outside the viewport
            instead of inside.
        L : label axis Logarithmically (see below).
        N : write Numeric labels in the conventional location below the
            viewport (X) or to the left of the viewport (Y).
        P : extend ("Project") major tick marks outside the box (ignored if
            option I is specified).
        M : write numeric labels in the unconventional location above the
            viewport (X) or to the right of the viewport (Y).
        T : draw major Tick marks at the major coordinate interval.
        S : draw minor tick marks (Subticks).
        V : orient numeric labels Vertically. This is only applicable to Y.
            The default is to write Y-labels parallel to the axis.
        1 : force decimal labelling, instead of automatic choice (see PGNUMB).
        2 : force exponential labelling, instead of automatic.
      
       To get a complete frame, specify BC in both XOPT and YOPT.
       Tick marks, if requested, are drawn on the axes or frame
       or both, depending which are requested. If none of ABC is specified,
       tick marks will not be drawn. When PGENV calls PGBOX, it sets both
       XOPT and YOPT according to the value of its parameter AXIS:
       -1: 'BC', 0: 'BCNST', 1: 'ABCNST', 2: 'ABCGNST'.
      
       For a logarithmic axis, the major tick interval is always 1.0. The
       numeric label is 10**(x) where x is the world coordinate at the
       tick mark. If subticks are requested, 8 subticks are drawn between
       each major tick at equal logarithmic intervals.
      
       To label an axis with time (days, hours, minutes, seconds) or
       angle (degrees, arcmin, arcsec), use routine PGTBOX.

Updates:      Oct 16, 1998: JPT automatically extracted from source.
              Oct 21, 1998: JPT record Y-label lenght for PGLAB.