contour.old(x, y, z, v=<<see below>>, nint=5, add=F, labex=<<see below>>)
z
is
evaluated.
length(x)
by
length(y)
giving the surface height at grid
points, i.e.,
z[i,j]
is evaluated at
x[i]
,
y[j]
.
The
rows
of
z
are indexed by
x
, and the
columns
by
y
.
Missing values (
NA
s) are allowed.
xyz
, say.
Components
xyz$x
,
xyz$y
and
xyz$z
will be used. In particular, the
result of
interp
is suitable as an argument to
contour.old
.
nint
lines are drawn which cover most of the
range of
z
. See the function
pretty
.
v
is specified.
TRUE
, contour lines are added to the
current plot. Use this to add contours with a different
labex
parameter, line type, etc., or to add contours to some other
type of plot.
labex
is
0
,
no labels are plotted on contours.
It is possible in some extreme cases for contour lines to cross when this
function is used.
This is one of the reasons to prefer the
contour
function.
rx <- range(ozone.xy$x) ry <- range(ozone.xy$y) usa(xlim=rx, ylim=ry, lty=2, col=2) i <- interp(ozone.xy$x, ozone.xy$y, ozone.median) contour.old(i, add=T, labex=0) text(ozone.xy, ozone.median) title(main="Median Ozone Concentrations in the North East")