anovaPlot: Graphical Anova

Description Usage Arguments Details Value warning Note Author(s) References See Also Examples

Description

Dots plot displaying the deviations of factor levels from the mean showing the residuals as reference distribution.

Usage

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    anovaPlot(obj, stacked = TRUE, base = TRUE, axes = TRUE,
    faclab = TRUE, labels = FALSE, cex = par("cex"),
    cex.lab = par("cex.lab"), ...)

Arguments

obj

Object of class aov or lm for which marginal deviations from the mean and the residuals distribution is displayed.

stacked

logical. If TRUE and if it is necessary the dots are stacked, otherwise all points are displayed at same level with possible overlapping.

base

logical. By default a base line is displayed for each factor. If FALSE this line is omitted.

axes

logical. By default a scaled axes is drawn for each factor. If FALSE the axes are omitted.

faclab

logical. By default factor effect names and ‘Residuals’ are used to label each dot plot. No axis is labelled otherwise.

labels

logical. By default, dots are used to the display. If labels=TRUE then factor levels are displayed for the factor dots plots and sequential enumeration is used for the residuals.

cex

numeric. Expansion factor of the character used for labelling the factor levels.

cex.lab

numeric. Expansion factor of the character used for labelling each factor.

...

additional parameters passed to the dots function.

Details

Dots plot are displayed for the scaled deviations of factor levels from the grand mean and the distribution of the residuals is shown at the bottom of the plot for graphical comparison. The scaled factor for the factor deviations is sqrt(n / k), where k and n are the factor and residuals degrees of freedom reported by anova(obj). If labels=TRUE then the factor levels are used for as points instead of dots. This option is useful to post labelling the dot plots. See dots function. The Anova plot is built in a (0,1)x(0,1) plot area. The area plot is divided to accommodate each of the factors and the residual at the bottom of the plotting area. The function returns a list with the coordinates of all the dots displayed.

Value

The function is called for graphical display of factor levels mean and residuals as reference distribution. An invisible list with the actual (x,y) coordinates used for each of the factors and residuals.

warning

The function identifies as an interaction factor any factor with the colon character ":" in its name. Factors like "I(A:B)" will give you problems.

Note

The anova plot presented here is thought for graphical comparison of factor effects in one-layer balanced designed experiments. The function is not prepared for general situations. However, representation of some simple split-plot experiments is possible.

Author(s)

Ernesto Barrios

References

Box G. E. P. (2000). Box on Quality. Edited by G. C. Tiao et al. New York: Wiley.

Box G. E. P, Hunter, J. S. and Hunter, W. C. (2005). Statistics for Experimenters II. New York: Wiley.

See Also

dots, dotPlot

Examples

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library(BHH2)
data(heads.data)
heads.data$periods <- factor(heads.data$periods)
heads.data$heads <- factor(heads.data$heads)

heads.aov <- aov(resp~periods+heads,data=heads.data)
anovaPlot(heads.aov)

anovaPlot(heads.aov,labels=TRUE,faclab=TRUE)


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