These functions are intended to replace common low level traditional
graphics functions, primarily for use in panel functions. The
originals can not be used (at least not easily) because lattice panel
functions need to use grid graphics. Low level drawing functions in
grid can be used directly as well, and is often more flexible. These
functions are provided for convenience and portability.
locations. x2 and
y2 are available for for S compatibility.
length, unit
determines extent of arrow head. length specifies the length
in terms of unit, which can be any valid grid unit as long as
it doesn't need a data argument. unit defaults to
inches, which is the only option in the base version of the
function, arrows.
angle, code, type, labels, srt, adj, pos, offset
arguments
controlling behaviour. See respective base functions for details.
For larrows and panel.larrows, type is either
"open" or "closed", indicating the type of
arrowhead.
ends
serves the same function as code, using
descriptive names rather than integer codes. If specified, this
overrides code
graphical
parameters. fill applies to points when pch is in
21:25 and specifies the fill color, similar to the bg
argument in the base graphics function points. For
devices that support alpha-transparency, a numeric argument
alpha between 0 and 1 can controls transparency. Be careful
with this, since for devices that do not support alpha-transparency,
nothing will be drawn at all if this is set to anything other than
0.
fill, font and fontface are included in
lpolygon and lsegments only to ensure that they are
not passed down (as gpar does not like them).
origin
for type="h" or type="H", the value to
which lines drop down.
xleft, ybottom, xright, ytop
see rect
width, height, just, hjust, vjust
finer control over
rectangles, see grid.rect
...
extra arguments, passed on to lower level functions as
appropriate.
identifier
A character string that is prepended to the name of the grob
that is created.
name.type
A character value indicating whether the name of the grob
should have panel or strip information added to it.
Typically either "panel", "strip",
"strip.left", or "" (for no extra information).
Details
These functions are meant to be grid replacements of the corresponding
base R graphics functions, to allow existing Trellis code to be used
with minimal modification. The functions panel.* are
essentally identical to the l* versions, are recommended for
use in new code (as opposed to ported code) as they have more readable
names.
See the documentation of the base functions for usage. Not all
arguments are always supported. All these correspond to the default
methods only.
Note
There is a new type="H" option wherever appropriate, which is
similar to type="h", but with horizontal lines.