Quantilecomparison plots
Description
Plots empirical quantiles of a variable against theoretical quantiles of a comparison distribution.
Usage
1 2 3 4 5 
Arguments
x 
vector of numeric values. 
distribution 
root name of comparison distribution – e.g., 
ylab 
label for vertical (empirical quantiles) axis. 
xlab 
label for horizontal (comparison quantiles) axis. 
main 
label for plot. 
envelope 
confidence level for pointwise confidence envelope, or

labels 
vector of point labels for interactive point identification,
or 
las 
if 
col 
color for points; the default is the fourth entry
in the current color palette (see 
lcol 
color for lines; the default is the second entry as above. 
xlim 
the x limits (x1, x2) of the plot. Note that x1 > x2 is allowed and leads to a reversed axis. 
ylim 
the y limits of the plot 
pch 
plotting character for points; default is 
bg 
background color of points 
cex 
factor for expanding the size of plotted symbols; the default is

lwd 
line width; default is 
line 

... 
arguments such as 
Details
Draws theoretical quantilecomparison plots for variables and for studentized residuals from a linear model. A comparison line is drawn on the plot either through the quartiles of the two distributions, or by robust regression.
Any distribution for which quantile and density functions exist in R (with prefixes
q
and d
, respectively) may be used.
Studentized residuals are plotted against the appropriate tdistribution.
This is adapted from qq.plot of package car with different values for points and lines, more options, more transparent code and examples in the current setting. Another similar but sophisticated function is qqmath of package lattice.
Value
NULL
. These functions are used only for their side effect (to make a graph).
Author(s)
John Fox, Jing Hua Zhao
References
Davison, A. C. (2003) Statistical Models. Cambridge University Press.
Leemis, L. M., J. T. Mcqueston (2008) Univariate distribution relationships. The American Statistician 62:4553
See Also
qqnorm
, qqunif
, gcontrol2
Examples
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