contour.im {spatstat.geom}

Contour plot of pixel image

Description

Generates a contour plot of a pixel image.

Usage

   ## S3 method for class 'im'
contour(x, ..., main, axes=FALSE, add=FALSE,
            nlevels=10, levels=NULL, labels=NULL, log=FALSE, 
            col=par("fg"), 
            clipwin=NULL, show.all=!add, do.plot=TRUE)

Arguments

x

Pixel image to be plotted. An object of class "im".

main

Character string to be displayed as the main title.

nlevels, levels

Arguments passed to contour.default controlling the choice of contour levels.

labels

Arguments passed to contour.default controlling the text labels plotted next to the contour lines.

log

Logical value. If TRUE, the contour levels will be evenly-spaced on a logarithmic scale.

axes

Logical. If TRUE, coordinate axes are plotted (with tick marks) around a region slightly larger than the image window. If FALSE (the default), no axes are plotted, and a box is drawn tightly around the image window. Ignored if add=TRUE.

add

Logical. If FALSE, a new plot is created. If TRUE, the contours are drawn over the existing plot.

col

Colour in which to draw the contour lines. Either a single value that can be interpreted as a colour value, or a colourmap object.

clipwin

Optional. A window (object of class "owin"). Only this subset of the data will be displayed.

...

Other arguments passed to contour.default controlling the contour plot; see Details.

show.all

Logical value indicating whether to display all plot elements including the main title, bounding box, and (if axis=TRUE) coordinate axis markings. Default is TRUE for new plots and FALSE for added plots.

do.plot

Logical value indicating whether to actually perform the plot.

Details

This is a method for the generic contour function, for objects of the class "im".

An object of class "im" represents a pixel image; see im.object.

This function displays the values of the pixel image x as a contour plot on the current plot device, using equal scales on the x and y axes.

The appearance of the plot can be modified using any of the arguments listed in the help for contour.default. Useful ones include:

nlevels

Number of contour levels to plot.

drawlabels

Whether to label the contour lines with text.

col,lty,lwd

Colour, type, and width of contour lines.

See contour.default for a full list of these arguments.

The defaults for any of the abovementioned arguments can be reset using spatstat.options("par.contour").

If log=TRUE, the contour lines will be evenly-spaced on a logarithmic scale, provided the range of pixel values is at least 1.5 orders of magnitude (a ratio of at least 32). Otherwise the levels will be evenly-spaced on the original scale.

If col is a colour map (object of class "colourmap", see colourmap) then the contours will be plotted in different colours as determined by the colour map. The contour at level z will be plotted in the colour col(z) associated with this level in the colour map.

Value

Invisibly, a rectangle (object of class "owin" specifying a rectangle) containing the plotted region.

Author(s)

Adrian Baddeley [e-mail], Rolf Turner [e-mail] and Ege Rubak [e-mail].

See Also

im.object, plot.im, persp.im

Examples

   # an image
   Z <- setcov(owin())
   contour(Z, axes=TRUE)
   contour(Z)

   V <- 100 * Z^2 + 1
   contour(V, log=TRUE, labcex=1)

   co <- colourmap(rainbow(100), range=c(0,1))
   contour(Z, col=co, lwd=2)