R: Plot Leverage Function

plot.leverage.ppm {spatstat.core} | R Documentation

## Plot Leverage Function

### Description

Generate a pixel image plot, or a contour plot, or a perspective plot, of a leverage function that has been computed by `leverage.ppm`.

### Usage

     ## S3 method for class 'leverage.ppm'
    plot(x, ...,
                                 what=c("smooth", "nearest", "exact"),
                                 showcut=TRUE,
                                 args.cut=list(drawlabels=FALSE),
                                 multiplot=TRUE)

     ## S3 method for class 'leverage.ppm'
    contour(x, ...,
                                 what=c("smooth", "nearest"),
                                 showcut=TRUE,
                                 args.cut=list(col=3, lwd=3, drawlabels=FALSE),
                                 multiplot=TRUE)

     ## S3 method for class 'leverage.ppm'
    persp(x, ...,
                   what=c("smooth", "nearest"),
                   main, zlab="leverage")

### Arguments

`x` | Leverage function (object of class `"leverage.ppm"`) computed by `leverage.ppm`.
`...` | Arguments passed to `plot.im` or `contour.im` or `persp.im` controlling the plot.
`what` | Character string (partially matched) specifying the values to be plotted. See Details.
`showcut` | Logical. If `TRUE`, a contour line is plotted at the level equal to the theoretical mean of the leverage.
`args.cut` | Optional list of arguments passed to `contour.default` to control the plotting of the contour line for the mean leverage.
`multiplot` | Logical value indicating whether it is permissible to display several plot panels.
`main` | Optional main title. A character string or character vector.
`zlab` | Label for the z axis. A character string.

### Details

These functions are the `plot`, `contour` and `persp` methods for objects of class `"leverage.ppm"`. Such objects are computed by the command `leverage.ppm`.

The `plot` method displays the leverage function as a colour pixel image using `plot.im`, and draws a single contour line at the mean leverage value using `contour.default`. Use the argument `clipwin` to restrict the plot to a subset of the full data.

The `contour` method displays the leverage function as a contour plot, and also draws a single contour line at the mean leverage value, using `contour.im`.

The `persp` method displays the leverage function as a surface in perspective view, using `persp.im`.

Since the exact values of leverage are computed only at a finite set of quadrature locations, there are several options for these plots:

`what="smooth"`:

  (the default) an image plot showing a smooth function, obtained by applying kernel smoothing to the exact leverage values;

`what="nearest"`:

  an image plot showing a piecewise-constant function, obtained by taking the exact leverage value at the nearest quadrature point;

`what="exact"`:

  a symbol plot showing the exact values of leverage as circles, centred at the quadrature points, with diameters proportional to leverage.

The pixel images are already contained in the object `x` and were computed by `leverage.ppm`; the resolution of these images is controlled by arguments to `leverage.ppm`.

### Value

Same as for `plot.im`, `contour.im` and `persp.im` respectively.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au, Rolf Turner r.turner@auckland.ac.nz and Ege Rubak rubak@math.aau.dk.

### References

Baddeley, A., Chang, Y.M. and Song, Y. (2013) Leverage and influence diagnostics for spatial point process models. Scandinavian Journal of Statistics 40, 86–104.

### See Also

`leverage.ppm`.

### Examples

    if(offline <- !interactive()) op <- spatstat.options(npixel=32, ndummy.min=16)

       X <- rpoispp(function(x,y) { exp(3+3*x) })
       fit <- ppm(X ~x+y)
       lef <- leverage(fit)
       plot(lef)
       contour(lef)
       persp(lef)

    if(offline) spatstat.options(op)

[Package spatstat.core version 2.3-0 Index]