Description Usage Arguments Details Value Author(s) References See Also Examples
Plots empirical quantiles of a variable, or of studentized residuals from a linear model, against theoretical quantiles of a comparison distribution.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | qqPlot(x, ...)
qqp(...)
## Default S3 method:
qqPlot(x, distribution="norm", ylab=deparse(substitute(x)),
xlab=paste(distribution, "quantiles"), main=NULL, las=par("las"),
envelope=.95, col=palette()[1], col.lines=palette()[2],
lwd=2, pch=1, cex=par("cex"),
line=c("quartiles", "robust", "none"), id=TRUE, grid=TRUE, ...)
## S3 method for class 'lm'
qqPlot(x, xlab=paste(distribution, "Quantiles"),
ylab=paste("Studentized Residuals(",
deparse(substitute(x)), ")", sep=""),
main=NULL, distribution=c("t", "norm"),
line=c("robust", "quartiles", "none"), las=par("las"),
simulate=TRUE, envelope=.95, reps=100,
col=palette()[1], col.lines=palette()[2], lwd=2, pch=1, cex=par("cex"),
id=TRUE, grid=TRUE, ...)
|
x |
vector of numeric values or |
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 point-wise confidence envelope, or
|
las |
if |
col |
color for points; the default is the first entry
in the current color palette (see |
col.lines |
color for lines; the default is the second entry in the current color palette. |
pch |
plotting character for points; default is |
cex |
factor for expanding the size of plotted symbols; the default is
|
id |
controls point identification; if |
lwd |
line width; default is |
line |
|
simulate |
if |
reps |
integer; number of bootstrap replications for confidence envelope. |
... |
arguments such as |
grid |
If TRUE, the default, a light-gray background grid is put on the graph |
Draws theoretical quantile-comparison 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.
When plotting a vector, the confidence envelope is based on the SEs of the order statistics
of an independent random sample from the comparison distribution (see Fox, 2008).
Studentized residuals from linear models are plotted against the appropriate t-distribution with a point-wise
confidence envelope computed by default by a parametric bootstrap,
as described by Atkinson (1985).
The function qqp
is an abbreviation for qqPlot
.
These functions return the labels of identified points.
John Fox jfox@mcmaster.ca
Fox, J. (2008) Applied Regression Analysis and Generalized Linear Models, Second Edition. Sage.
Fox, J. and Weisberg, S. (2011) An R Companion to Applied Regression, Second Edition, Sage.
Atkinson, A. C. (1985) Plots, Transformations, and Regression. Oxford.
qqplot
, qqnorm
,
qqline
, showLabels
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