bagplot {aplpack}R Documentation

bagplot, a bivariate boxplot

Description

compute.bagplot() computes an object describing a bagplot of a bivariate data set. plot.bagplot() plots a bagplot object. bagplot() computes and plots a bagplot.

Usage

bagplot(x, y, factor = 3, na.rm = FALSE, approx.limit = 300,  
       show.outlier = TRUE, show.whiskers = TRUE, 
       show.looppoints = TRUE, show.bagpoints = TRUE,
       show.loophull = TRUE, show.baghull = TRUE, 
       create.plot = TRUE, add = FALSE, pch = 16, cex = 0.4, 
       dkmethod = 2, precision = 1, verbose = FALSE, 
       debug.plots = "no",   col.loophull="#aaccff", 
       col.looppoints="#3355ff", col.baghull="#7799ff", 
       col.bagpoints="#000088", transparency=FALSE, ...
)
compute.bagplot(x, y, factor = 3, na.rm = FALSE, approx.limit = 300, 
       dkmethod=2,precision=1,verbose=FALSE,debug.plots="no")
plot.bagplot(x,  
       show.outlier = TRUE, show.whiskers = TRUE, 
       show.looppoints = TRUE, show.bagpoints = TRUE,
       show.loophull = TRUE, show.baghull = TRUE, 
       add = FALSE, pch = 16, cex = 0.4, verbose = FALSE, 
       col.loophull="#aaccff", col.looppoints="#3355ff", 
       col.baghull="#7799ff", col.bagpoints="#000088", 
       transparency=FALSE,...)

Arguments

x x values of a data set; in bagplot: an object of class bagplot computed by compute.bagplot
y y values of the data set
factor factor defining the loop
na.rm if TRUE 'NA' values are removed otherwise exchanged by mean
approx.limit if the number of data points exceeds approx.limit a sample is used to compute some of the quantities; default: 300
show.outlier if TRUE outlier are shown
show.whiskers if TRUE whiskers are shown
show.looppoints if TRUE loop points are plottet
show.bagpoints if TRUE bag points are plottet
show.loophull if TRUE the loop is plotted
show.baghull if TRUE the bag is plotted
create.plot if FALSE no plot is created
add if TRUE the bagplot is added to an existing plot
pch sets the plotting character
cex sets characters size
dkmethod 1 or 2, there are two method of approximating the bag, method 1 is very rough
precision precision of approximation, default: 1
verbose automatic commenting of calculations
debug.plots if TRUE additional plots describing intermediate results are constructed
col.loophull color of loop hull
col.looppoints color of the points of the loop
col.baghull color of bag hull
col.bagpoints color of the points of the bag
transparency see section details
... additional graphical parameters

Details

A bagplot is a bivariate generalization of the well known boxplot. It has been proposed by Rousseeuw, Ruts, and Tukey. In the bivariate case the box of the boxplot changes to a convex polygon, the bag of bagplot. In the bag are 50 percent of all points. The fence separates points within the fence from points outside. It is computed by increasing the the bag. The loop is defined as the convex hull containing all points inside the fence. If all points are on a straight line you get a classical boxplot. bagplot() plots bagplots that are very similar to the one described in Rousseeuw et al. Remarks: The two dimensional median is approximated. For large data sets the error will be very small. On the other hand it is not very wise to make a (graphical) summary of e.g. 10 bivariate data points. In case you want to plot multiple (overlapping) bagplots, you may want plots that are semi-transparent. For this you can use the transparency flag. If transparency==TRUE the alpha layer is set to '99' (hex). This causes the bagplots to appear semi-transparent, but ONLY if the output device is PDF and opened using: pdf(file="filename.pdf", version="1.4"). For this reason, the default is transparency==FALSE. This feature as well as the arguments to specify different colors has been proposed by Wouter Meuleman.

Value

compute.bagplot returns an object of class bagplot that could be plotted by plot.bagplot().

Note

Version of bagplot: 08/2007

Author(s)

Peter Wolf

References

P. J. Rousseeuw, I. Ruts, J. W. Tukey (1999): The bagplot: a bivariate boxplot, The American Statistician, vol. 53, no. 4, 382–387

See Also

boxplot

Examples

  # example: 100 random points and one outlier
  dat<-cbind(rnorm(100)+100,rnorm(100)+300)
  dat<-rbind(dat,c(105,295))
  bagplot(dat,factor=2.5,create.plot=TRUE,approx.limit=300,
     show.outlier=TRUE,show.looppoints=TRUE,
     show.bagpoints=TRUE,dkmethod=2,
     show.whiskers=TRUE,show.loophull=TRUE,
     show.baghull=TRUE,verbose=FALSE)
  # example of Rousseeuw et al., see R-package rpart
  cardata <- structure(as.integer( c(2560,2345,1845,2260,2440,
   2285, 2275, 2350, 2295, 1900, 2390, 2075, 2330, 3320, 2885,
   3310, 2695, 2170, 2710, 2775, 2840, 2485, 2670, 2640, 2655,
   3065, 2750, 2920, 2780, 2745, 3110, 2920, 2645, 2575, 2935,
   2920, 2985, 3265, 2880, 2975, 3450, 3145, 3190, 3610, 2885,
   3480, 3200, 2765, 3220, 3480, 3325, 3855, 3850, 3195, 3735,
   3665, 3735, 3415, 3185, 3690, 97, 114, 81, 91, 113, 97, 97,
   98, 109, 73, 97, 89, 109, 305, 153, 302, 133, 97, 125, 146,
   107, 109, 121, 151, 133, 181, 141, 132, 133, 122, 181, 146,
   151, 116, 135, 122, 141, 163, 151, 153, 202, 180, 182, 232,
   143, 180, 180, 151, 189, 180, 231, 305, 302, 151, 202, 182,
   181, 143, 146, 146)), .Dim = as.integer(c(60, 2)), 
   .Dimnames = list(NULL, c("Weight", "Disp.")))
  bagplot(cardata,factor=3,show.baghull=TRUE,
    show.loophull=TRUE,precision=1,dkmethod=2)
  title("car data Chambers/Hastie 1992")
  # points of y=x*x
  bagplot(x=1:30,y=(1:30)^2,verbose=FALSE,dkmethod=2)
  # one dimensional subspace
  bagplot(x=1:100,y=1:100)

[Package aplpack version 1.1.1 Index]