| qq.plot {car} | R Documentation |
Plots empirical quantiles of a variable, or of studentized residuals from a linear model, against theoretical quantiles of a comparison distribution.
qq.plot(x, ...)
qqp(...)
## Default S3 method:
qq.plot(x, distribution="norm", ylab=deparse(substitute(x)),
xlab=paste(distribution, "quantiles"), main=NULL, las=par("las"),
envelope=.95, labels=FALSE, col=palette()[2], lwd=2, pch=1, cex=1,
line=c("quartiles", "robust", "none"), ...)
## S3 method for class 'lm':
qq.plot(x, main=NULL, xlab=paste(distribution, "Quantiles"),
ylab=paste("Studentized Residuals(", deparse(substitute(x)), ")",
sep = ""),
distribution=c("t", "norm"), line=c("quartiles", "robust", "none"),
las=par('las'), simulate=FALSE, envelope=0.95, labels=names(rstudent),
reps=100, col=palette()[2], lwd=2, pch=1, cex=1, ...)
x |
vector of numeric values or lm object. |
distribution |
root name of comparison distribution – e.g., norm for the
normal distribution; t for the t-distribution. |
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
FALSE for no envelope. |
labels |
vector of point labels for interactive point identification,
or FALSE for no labels. |
las |
if 0, ticks labels are drawn parallel to the
axis; set to 1 for horizontal labels (see par). |
col |
color for points and lines; the default is the second entry
in the current color palette (see palette
and par). |
pch |
plotting character for points; default is 1
(a circle, see par). |
cex |
factor for expanding the size of plotted symbols; the default is
1. |
lwd |
line width; default is 2 (see par).
Confidence envelopes are drawn at half this line width. |
line |
"quartiles" to pass a line through the quartile-pairs, or
"robust" for a robust-regression line; the latter uses the rlm
function in the MASS package. Specifying line = "none" suppresses the line. |
simulate |
if TRUE calculate confidence envelope by parametric bootstrap;
for lm object only. The method is due to Atkinson (1985). |
reps |
integer; number of bootstrap replications for confidence envelope. |
... |
arguments such as df to be passed to the appropriate quantile function. |
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.
Studentized residuals are plotted against the
appropriate t-distribution.
The function qqp is an abbreviation for qq.plot.
NULL. These functions are used only for their side effect (to make a graph).
John Fox jfox@mcmaster.ca
Fox, J. (1997) Applied Regression, Linear Models, and Related Methods. Sage.
Atkinson, A. C. (1985) Plots, Transformations, and Regression. Oxford.
x<-rchisq(100, df=2) qq.plot(x) qq.plot(x, dist="chisq", df=2) qq.plot(lm(interlocks~assets+sector+nation, data=Ornstein), sim=TRUE)