spreadLevelPlot {car} | R Documentation |
Creates plots for examining the possible dependence of spread on level, or an extension of these plots to the studentized residuals from linear models.
spreadLevelPlot(x, ...)
slp(...)
## S3 method for class 'formula'
spreadLevelPlot(x, data=NULL, subset, na.action,
main=paste("Spread-Level Plot for", varnames[response],
"by", varnames[-response]), ...)
## Default S3 method:
spreadLevelPlot(x, by, robust.line=TRUE,
start=0, xlab="Median", ylab="Hinge-Spread", point.labels=TRUE, las=par("las"),
main=paste("Spread-Level Plot for", deparse(substitute(x)),
"by", deparse(substitute(by))), col=palette()[1], col.lines=palette()[2],
pch=1, lwd=2, grid=TRUE, ...)
## S3 method for class 'lm'
spreadLevelPlot(x, robust.line=TRUE,
xlab="Fitted Values",
ylab="Absolute Studentized Residuals", las=par("las"),
main=paste("Spread-Level Plot for\n", deparse(substitute(x))),
pch=1, col=palette()[1], col.lines=palette()[2], lwd=2, grid=TRUE, ...)
## S3 method for class 'spreadLevelPlot'
print(x, ...)
x |
a formula of the form |
data |
an optional data frame containing the variables to be plotted.
By default the variables are taken from the environment from which
|
subset |
an optional vector specifying a subset of observations to be used. |
na.action |
a function that indicates what should happen when the data contain |
by |
a factor, numeric vector, or character vector defining groups. |
robust.line |
if |
start |
add the constant |
main |
title for the plot. |
xlab |
label for horizontal axis. |
ylab |
label for vertical axis. |
point.labels |
if |
las |
if |
col |
color for points; the default is the first entry
in the current color palette (see |
col.lines |
color for lines; default is the second entry in the current palette |
pch |
plotting character for points; default is |
lwd |
line width; default is |
grid |
If TRUE, the default, a light-gray background grid is put on the graph |
... |
arguments passed to plotting functions. |
Except for linear models, computes the statistics for, and plots, a Tukey spread-level plot of log(hinge-spread) vs. log(median) for the groups; fits a line to the plot; and calculates a spread-stabilizing transformation from the slope of the line.
For linear models, plots log(abs(studentized residuals) vs. log(fitted values).
The function slp
is an abbreviation for spreadLevelPlot
.
An object of class spreadLevelPlot
containing:
Statistics |
a matrix with the lower-hinge, median, upper-hinge, and hinge-spread
for each group. (Not for an |
PowerTransformation |
spread-stabilizing power transformation, calculated as |
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.
Hoaglin, D. C., Mosteller, F. and Tukey, J. W. (Eds.) (1983) Understanding Robust and Exploratory Data Analysis. Wiley.
spreadLevelPlot(interlocks + 1 ~ nation, data=Ornstein)
slp(lm(interlocks + 1 ~ assets + sector + nation, data=Ornstein))