R: Scatterplot Matrix for Pixel Images

pairs.im {spatstat} | R Documentation

## Scatterplot Matrix for Pixel Images

### Description

Produces a scatterplot matrix of the pixel values in two or more pixel images.

### Usage

    ## S3 method for class 'im'
    pairs(..., plot=TRUE)

### Arguments

`...` | Any number of arguments, each of which is either a pixel image (object of class `"im"`) or a named argument to be passed to `pairs.default`.
`plot` | Logical. If `TRUE`, the scatterplot matrix is plotted.

### Details

This is a method for the generic function `pairs` for the class of pixel images.

It produces a square array of plot panels, in which each panel shows a scatterplot of the pixel values of one image against the corresponding pixel values of another image.

At least two of the arguments `...` should be pixel images (objects of class `"im"`). Their spatial domains must overlap, but need not have the same pixel dimensions.

First the pixel image domains are intersected, and converted to a common pixel resolution. Then the corresponding pixel values of each image are extracted. Then `pairs.default` is called to plot the scatterplot matrix.

Any arguments in `...` which are not pixel images will be passed to `pairs.default` to control the plot.

### Value

Invisible. A `data.frame` containing the corresponding pixel values for each image. The return value also belongs to the class `plotpairsim` which has a plot method, so that it can be re-plotted.

### Image or Contour Plots

Since the scatterplots may show very dense concentrations of points, it may be useful to set `panel=panel.image` or `panel=panel.contour` to draw a colour image or contour plot of the kernel-smoothed density of the scatterplot in each panel. The argument `panel` is passed to `pairs.default`. See the help for `panel.image` and `panel.contour`.

### Low Level Control of Graphics

To control the appearance of the individual scatterplot panels, see `pairs.default`, `points` or `par`. To control the plotting symbol for the points in the scatterplot, use the arguments `pch`, `col`, `bg` as described under `points` (because the default panel plotter is the function `points`). To suppress the tick marks on the plot axes, type `par(xaxt="n", yaxt="n")` before calling `pairs`.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

`pairs`, `pairs.default`, `panel.contour`, `panel.image`, `plot.im`, `im`, `par`

### Examples

      X <- density(rpoispp(30))
      Y <- density(rpoispp(40))
      Z <- density(rpoispp(30))
      pairs(X,Y,Z)

[Package spatstat version 1.54-0 Index]