This function is similar to grid
in classic graphics,
except that it draws a 3D grid in the plot.
The grid is drawn in a plane perpendicular to the coordinate axes. The
first letter of the side
argument specifies the direction of
the plane: "x"
, "y"
or "z"
(or uppercase
versions) to specify the coordinate which is constant on the plane.
If at = NULL
(the default), the grid is drawn at the limit of
the box around the data. If the second letter of the side
argument
is "-"
or is not present, it is the lower limit; if "+"
then at the upper limit. The grid lines are drawn at values
chosen by pretty
with n
suggested locations.
The default locations should match those chosen by axis3d
with nticks = n
.
If at
is a numeric vector, the grid lines are drawn at those values.
If at
is a list, then the "x"
component is used to
specify the x location, the "y"
component specifies the y location, and
the "z"
component specifies the z location. Missing components
are handled using the default as for at = NULL
.
Multiple grids may be drawn by specifying multiple values for side
or for the component of at
that specifies the grid location.