# contourLines

##### Calculate Contour Lines

Calculate contour lines for a given set of data.

- Keywords
- dplot

##### 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:

The contour level.

The x-coordinates of the contour.

The y-coordinates of the contour.

##### See Also

`options("max.contour.segments")`

for the maximal
complexity of a single contour line.

##### Examples

`library(grDevices)`

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

*Documentation reproduced from package grDevices, version 3.4.1, License: Part of R 3.4.1*