X and Y Axes

# :call-seq:
#   show_bottom_edge
#
# If the flag bottom_edge_visible is +true+ and the xaxis_loc is not +BOTTOM+, then
# shows the bottom edge of the frame.  Otherwise, simply returns.

# :call-seq:
#   show_left_edge
#
# If the flag left_edge_visible is +true+ and the yaxis_loc is not +LEFT+, then
# shows the left edge of the frame.  Otherwise, simply returns.

# :call-seq:
#   show_right_edge
#
# If the flag right_edge_visible is +true+ and the yaxis_loc is not +RIGHT+, then
# shows the right edge of the frame.  Otherwise, simply returns.

# :call-seq:
#   show_top_edge
#
# If the flag top_edge_visible is +true+ and the xaxis_loc is not +TOP+, then
# shows the top edge of the frame.  Otherwise, simply returns.

# :call-seq:
#   show_xaxis
#
# If the flag xaxis_visible is currently +true+, then this routine shows the x axis
# at the location specified by xaxis_loc.  If the flag is +false+, it simply returns.

# :call-seq:
#   show_yaxis
#
# If the flag yaxis_visible is currently +true+, then this routine shows the y axis
# at the location specified by yaxis_loc.  If the flag is +false+, it simply returns.

Determines the axis type to use when showing the bottom edge of a plot.
Valid types are the following predefined constants: AXIS_HIDDEN,
AXIS_LINE_ONLY, AXIS_WITH_MAJOR_TICKS_ONLY, AXIS_WITH_TICKS_ONLY,
AXIS_WITH_MAJOR_TICKS_AND_NUMERIC_LABELS, and
AXIS_WITH_TICKS_AND_NUMERIC_LABELS.

If True, then it is okay for tioga to show the bottom edge of a plot.
If False, then calls on show_bottom_edge return immediately.  This
attribute is "one-way-only" in that it starts True and can be set
False, but cannot be reset to True except by restoring the graphics
state in which is was still True.  This is intended to help control the
behavior of plots when embedded as subplots in a larger configuration.
Note that this does not effect showing the x axis on the bottom; it only
applies to calls on show_bottom_edge.

Determines the axis type to use when showing the top edge of a plot.
Valid types are the following predefined constants: AXIS_HIDDEN,
AXIS_LINE_ONLY, AXIS_WITH_MAJOR_TICKS_ONLY, AXIS_WITH_TICKS_ONLY,
AXIS_WITH_MAJOR_TICKS_AND_NUMERIC_LABELS, and
AXIS_WITH_TICKS_AND_NUMERIC_LABELS.

If True, then it is okay for tioga to show the top edge of a plot.  If
False, then calls on show_top_edge return immediately.  This attribute
is "one-way-only" in that it starts True and can be set False, but
cannot be reset to True except by restoring the graphics state in which
is was still True.  This is intended to help control the behavior of
plots when embedded as subplots in a larger configuration.  Note that
this does not effect showing the x axis on the top; it only applies to
calls on show_top_edge.