R: Calculate Contour Lines

contourLines {grDevices} | R Documentation

## 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

`x,y` | locations of grid lines at which the values in `z` are measured. These must be in ascending order. By default, equally spaced values from 0 to 1 are used. If `x` is a `list`, its components `x$x` and `x$y` are used for `x` and `y`, respectively. If the list has component `z` this is used for `z`.
`z` | a matrix containing the values to be plotted (`NA`s are allowed). Note that `x` can be used instead of `z` for convenience.
`nlevels` | number of contour levels desired iff `levels` is not supplied.
`levels` | numeric vector of levels at which to draw contour lines.

### Details

`contourLines` draws nothing, but returns a set of contour lines.

There is currently no documentation about the algorithm. The source code is in ‘R_HOME/src/main/plot3d.c’.

### Value

A list of contours. Each contour is a list with elements:

`level` | The contour level.
`x` | The x-coordinates of the contour.
`y` | The y-coordinates of the contour.

### See Also

`options("max.contour.segments")` for the maximal complexity of a single contour line.

`contour`.

### Examples

    x <- 10*1:nrow(volcano)
    y <- 10*1:ncol(volcano)
    contourLines(x, y, volcano)

[Package grDevices version 2.15.1 Index]