Name:         PGENV

Purpose:      set window and viewport and draw labeled frame

Category:     GRAPHICS

File:         pgplot.src

Author:       T.J. Pearson

Use:          see description below.

Description:

            SUBROUTINE PGENV (XMIN, XMAX, YMIN, YMAX, JUST, AXIS)
            REAL XMIN, XMAX, YMIN, YMAX
            INTEGER JUST, AXIS
      
       Set PGPLOT "Plotter Environment".  PGENV establishes the scaling
       for subsequent calls to PGPT, PGLINE, etc.  The plotter is
       advanced to a new page or panel, clearing the screen if necessary.
       If the "prompt state" is ON (see PGASK), confirmation
       is requested from the user before clearing the screen.
       If requested, a box, axes, labels, etc. are drawn according to
       the setting of argument AXIS.
      
       Arguments:
        XMIN   (input)  : the world x-coordinate at the bottom left corner
                          of the viewport.
        XMAX   (input)  : the world x-coordinate at the top right corner
                          of the viewport (note XMAX may be less than XMIN).
        YMIN   (input)  : the world y-coordinate at the bottom left corner
                          of the viewport.
        YMAX   (input)  : the world y-coordinate at the top right corner
                          of the viewport (note YMAX may be less than YMIN).
        JUST   (input)  : if JUST=1, the scales of the x and y axes (in
                          world coordinates per inch) will be equal,
                          otherwise they will be scaled independently.
        AXIS   (input)  : controls the plotting of axes, tick marks, etc:
            AXIS = -2 : draw no box, axes or labels;
            AXIS = -1 : draw box only;
            AXIS =  0 : draw box and label it with coordinates;
            AXIS =  1 : same as AXIS=0, but also draw the
                        coordinate axes (X=0, Y=0);
            AXIS =  2 : same as AXIS=1, but also draw grid lines
                        at major increments of the coordinates;
            AXIS = 10 : draw box and label X-axis logarithmically;
            AXIS = 20 : draw box and label Y-axis logarithmically;
            AXIS = 30 : draw box and label both axes logarithmically.
      
       For other axis options, use routine PGBOX. PGENV can be persuaded to
       call PGBOX with additional axis options by defining an environment
       parameter PGPLOT_ENVOPT containing the required option codes. 
       Examples:
         PGPLOT_ENVOPT=P      ! draw Projecting tick marks
         PGPLOT_ENVOPT=I      ! Invert the tick marks
         PGPLOT_ENVOPT=IV     ! Invert tick marks and label y Vertically

Updates:      Oct 16, 1998: JPT automatically extracted from source.