| % File src/library/grDevices/man/contourLines.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2008 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{contourLines} |
| \alias{contourLines} |
| \title{Calculate Contour Lines} |
| \description{ |
| Calculate contour lines for a given set of data. |
| } |
| \usage{ |
| contourLines(x = seq(0, 1, length.out = nrow(z)), |
| y = seq(0, 1, length.out = ncol(z)), |
| z, nlevels = 10, |
| levels = pretty(range(z, na.rm = TRUE), nlevels)) |
| } |
| \arguments{ |
| \item{x, y}{locations of grid lines at which the values in \code{z} are |
| measured. These must be in ascending order. By default, equally |
| spaced values from 0 to 1 are used. If \code{x} is a \code{list}, |
| its components \code{x$x} and \code{x$y} are used for \code{x} |
| and \code{y}, respectively. If the list has component \code{z} this |
| is used for \code{z}.} |
| \item{z}{a matrix containing the values to be plotted (\code{NA}s are |
| allowed). Note that \code{x} can be used instead of \code{z} for |
| convenience.} |
| \item{nlevels}{number of contour levels desired \bold{iff} |
| \code{levels} is not supplied.} |
| \item{levels}{numeric vector of levels at which to draw contour |
| lines.} |
| } |
| \details{ |
| \code{contourLines} draws nothing, but returns a set of contour lines. |
| |
| There is currently no documentation about the algorithm. |
| The source code is in \file{\var{\link{R_HOME}}/src/main/plot3d.c}. |
| } |
| \value{ |
| A list of contours. |
| Each contour is a list with elements: |
| \item{level }{The contour level.} |
| \item{x }{The x-coordinates of the contour.} |
| \item{y }{The y-coordinates of the contour.} |
| } |
| \seealso{ |
| \code{\link{options}("max.contour.segments")} for the maximal |
| complexity of a single contour line. |
| |
| \code{\link{contour}}. |
| } |
| \examples{ |
| x <- 10*1:nrow(volcano) |
| y <- 10*1:ncol(volcano) |
| contourLines(x, y, volcano) |
| } |
| \keyword{dplot} |