.BG
.VE $Header: /usr3/s/current/s/.help/RCS/contour,v 1.2 83/12/30 19:26:33 rab Exp $
.FN contour
.TL
contour: Contour Plotting
.CS
contour(x, y, z, v, nint=, add=, labex=)
.PP
.AG x
vector containing x coordinates of grid over which `z' is
evaluated.
.AG y
vector of grid y coordinates.
.AG z
matrix `len(x)' by `len(y)' giving 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 (NAs) are allowed.
.AG v
vector of heights of contour lines.  By default,
approximately `nint' lines are drawn which cover most of the
range of `z'.  See the function `pretty'.
.AG nint=
the approximate number of contour intervals desired, default
5.  Not needed if `v' is specified.
.AG add=
flag which if TRUE causes contour lines to be added to the
current plot. Useful for adding contours with different
`labex' parameter, line type, etc. Default FALSE.
.AG labex=
the desired size of the labels on contour lines, default is
same as standard (`cex') character size.  If `labex' is 0,
no labels are used.
.PP
Graphical parameters may also be supplied as arguments to this
function (see `par').
.PP
The first argument may be a structure containing components named `x',
`y', and `z'.
.EX
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(i,add=T,labex=0)
text(ozone.xy,ozone.median)
title(main="Median Ozone Concentrations in the North East")
.PI
.KW plot*
.KW multivariate
.KW aplot*
.KW hplot*
.WR
