ancovaplot

0th

Percentile

Analysis of Covariance Plots

Analysis of Covariance Plots. Any of the ancova models y ~ x * t y ~ t * x y ~ x + t y ~ t + x y ~ x , groups=t y ~ t, x=x y ~ x * t, groups=b y ~ t * x, groups=b y ~ x + t, groups=b y ~ t + x, groups=b

Keywords
models, hplot, regression, dplot
Usage
ancovaplot(object, ...)
## S3 method for class 'formula':
ancovaplot(object, data, groups=NULL, x=NULL, ...,
           formula=object,
           col=rep(tpg$col,
             length=length(levels(as.factor(groups)))),
           pch=rep(c(15,19,17,18,16,20, 0:14),
             length=length(levels(as.factor(groups)))),
           slope, intercept,
           layout=c(length(levels(cc)), 1),
           col.line=col, lty=1,
           superpose.panel=TRUE,
           between=if (superpose.panel)
                      list(x=c(rep(0, length(levels(cc))-1), 1))
                   else
                      list(x=0),
           col.by.groups=FALSE ## ignored unless groups= is specified
           )

panel.ancova.superpose(x, y, subscripts, groups, slope, intercept, col, pch, ..., col.line, lty, superpose.panel, col.by.groups, condition.factor, groups.cc.incompatible, plot.resids=FALSE, print.resids=FALSE, mean.x.line=FALSE, col.mean.x.line="gray80")

Arguments
formula, object
formula specifying the aov model. The function modifies it for the xyplot specification.
data
data.frame
groups
If the treatment factor is included in the formula, then groups is not needed. By default groups will be set to the treatment factor, but the user may specify another factor for groups, usually
x
Covariate. Required by ancovaplot.formula if the covariate is not included in the formula.

For panel.ancova.superpose, see panel.superpose.

...
Other arguments to be passed to xyplot.
col, pch
Standard lattice arguments. pch follows the value of groups. When col.by.groups is TRUE, then col follow the value of groups. When col.by.groups is
slope, intercept
Vector, the length of the number of treatment levels, containing slope and intercept of the abline in each panel. This is by default calculated based on the formula. The user may override each independently.
layout, between
Standard lattice arguments.
col.line, lty
Standard lattice arguments. By default, they follow the value of the treatment factor in the formula. col.line is recycled to the number of panels in the plot.
y, subscripts
See panel.xyplot.
superpose.panel
logical. if TRUE (the default), there is an additional panel on the right containing the superposition of the points and lines for all treatment levels.
col.by.groups
logical. See the discussion in argument col.
condition.factor, groups.cc.incompatible
These are both internal variables. condition.factor contains a copy of the treatment factor. groups.cc.incompatible is a logical which is set to TRUE when the groups argument is explicitly set by
plot.resids, print.resids, mean.x.line, col.mean.x.line
logical, logical, logical or numeric, color name. When plot.resids==TRUE then vertical line segments connecting the data points and the fitted line are drawn. The other two arguments are interpreted only when plot.resids==TRUE
Details

llll{ ancova=aov specification xyplot specification abline y ~ x * t y ~ x | t, groups=t lm(y[t] ~ x[t]) ## separate lines y ~ t * x y ~ x | t, groups=t lm(y[t] ~ x[t]) ## separate lines y ~ x + t y ~ x | t, groups=t lm(y ~ x + t) ## parallel lines y ~ t + x y ~ x | t, groups=t lm(y ~ x + t) ## parallel lines y ~ x , groups=t y ~ x | t, groups=t lm(y ~ x) ## single regression line y ~ t, x=x y ~ x | t, groups=t mean(t) ## separate horizontal lines y ~ x * t, groups=b y ~ x | t, groups=b lm(y[t] ~ x[t]) ## sep lines, pch&col follow b y ~ t * x, groups=b y ~ x | t, groups=b lm(y[t] ~ x[t]) ## sep lines, pch&col follow b y ~ x + t, groups=b y ~ x | t, groups=b lm(y ~ x + t) ## par lines, pch&col follow b y ~ t + x, groups=b y ~ x | t, groups=b lm(y ~ x + t) ## par lines, pch&col follow b }

Value

  • ancovaplot returns a c("ancova","trellis") object. panel.ancova.superpose is an ordinary lattice panel function.

References

Heiberger, Richard M. and Holland, Burt (2004). Statistical Analysis and Data Display: An Intermediate Course with Examples in S-Plus, R, and SAS. Springer Texts in Statistics. Springer. ISBN 0-387-40270-5.

See Also

See the older ancova.

Aliases
  • ancovaplot
  • ancovaplot.formula
  • panel.ancova.superpose
Examples
data(hotdog, package="HH")
  ancovaplot(Sodium ~ Calories + Type, data=hotdog)
  ancovaplot(Sodium ~ Calories * Type, data=hotdog)
  ancovaplot(Sodium ~ Calories, groups=Type, data=hotdog)
  ancovaplot(Sodium ~ Type, x=Calories, data=hotdog)

  ## Please see demo("ancova", package="HH") to coordinate placement
  ## of all four of these plots on the same page.

  ancovaplot(Sodium ~ Calories + Type, data=hotdog, plot.resids=TRUE)
Documentation reproduced from package HH, version 3.1-25, License: GPL (>= 2)

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