plot.lmrob: Plot Method for "lmrob" Objects

Description

Diagnostic plots for elements of class lmrob

Usage

# S3 method for lmrob
plot(x, which = 1:5,
     caption = c("Standardized residuals vs. Robust Distances",
   "Normal Q-Q vs. Residuals", "Response vs. Fitted Values",
   "Residuals vs. Fitted Values" , "Sqrt of abs(Residuals) vs. Fitted Values"),
   panel = if(add.smooth) panel.smooth else points,
   sub.caption = deparse(x$call), main = "",
   compute.MD = TRUE,
   ask = prod(par("mfcol")) < length(which) && dev.interactive(),
   id.n = 3, labels.id = names(residuals(x)), cex.id = 0.75,
   label.pos = c(4,2), qqline = TRUE, add.smooth = getOption("add.smooth"),
   ..., p=0.025)

Arguments

x: an object as created by lmrob
which: integer number between 1 and 5 to specify which plot is desired
caption: Caption for the different plots
panel: panel function. The useful alternative to points, panel.smooth can be chosen by add.smooth = TRUE.
main: main title
sub.caption: sub titles
compute.MD: logical indicating if the robust Mahalanobis distances should be recomputed, using covMcd() when needed, i.e., if which contains 1.
ask: waits for user input before displaying each plot
id.n: number of points to be labelled in each plot, starting with the most extreme.
labels.id: vector of labels, from which the labels for extreme points will be chosen. NULL uses observation numbers.
cex.id: magnification of point labels.
label.pos: positioning of labels, for the left half and right half of the graph respectively.

qqline: logical indicating if a qqline() should be added to the normal Q-Q plot.
add.smooth: logical indicating if a smoother should be added to most plots; see also panel above.
...: optional arguments for par, title, etc.
p: threshold for distance-distance plot

Details

if compute.MD = TRUE and the robust Mahalanobis distances need to be computed, they are stored (“cached”) with the object x when this function has been called from top-level.

References

Robust diagnostic plots as in Rousseeuw and van Zomeren (1990), see ‘References’ in ltsPlot.

Examples

Run this code

data(starsCYG)
## Plot simple data and fitted lines
plot(starsCYG)
 lmST <-    lm(log.light ~ log.Te, data = starsCYG)
RlmST <- lmrob(log.light ~ log.Te, data = starsCYG)
RlmST
abline(lmST, col = "red")
abline(RlmST, col = "blue")

op <- par(mfrow = c(2,2), mgp = c(1.5, 0.6, 0), mar= .1+c(3,3,3,1))
plot(RlmST, which = c(1:2, 4:5))
par(op)