Calculate Contour Lines

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Description

Calculate contour lines for a given set of data.

Usage

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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 (NAs 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

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

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