heplots (version 1.7.3)

colDevs: Calculate column deviations from central values

Description

colDevs calculates the column deviations of data values from a central value (mean, median, etc.), possibly stratified by a grouping variable.

Usage

colDevs(x, group, center = mean, group.var = FALSE, ...)

Value

By default, it returns a numeric matrix containing the deviations from the centering function. If levels==TRUE, it returns a data.frame containing the group factor prepended to the matrix of deviations.

Arguments

x

A numeric data frame or matrix.

group

A factor (or variable that can be coerced to a factor) indicating the membership of each observation in x in one or more groups. If missing, all the data is treated as a single group. You can also specify the interaction of two or more factors.

center

A function used to center the values (for each group if group is specified. The function must take a vector argument and return a scalar result.

group.var

logical. If TRUE, the group variable containing factor levels is prepended to the matrix of deviations.

...

Arguments passed down

Author

Michael Friendly

Details

Conceptually, the function is similar to a column-wise sweep, by group, allowing an arbitrary center function.

Non-numeric columns of x are removed, with a warning.

See Also

colMeans for column means,

sweep

Examples

data(iris)

Species <- iris$Species
irisdev <- colDevs(iris[,1:4], Species, mean)

irisdev <- colDevs(iris[,1:4], Species, median)
# trimmed mean, using an anonymous function
irisdev <- colDevs(iris[,1:4], Species, function(x) mean(x, trim=0.25))

# include the group factor in output
irisdev <- colDevs(iris[,1:4], Species, group.var = "Species")
head(irisdev)

# no grouping variable: deviations from column grand means
# include all variables (but suppress warning for this doc)
irisdev <- suppressWarnings( colDevs(iris) )

# two-way design
colDevs(Plastic[,1:3], Plastic[,"rate"])
colDevs(Plastic[,1:3], Plastic[,"additive"])
# cell deviations
#' colDevs(Plastic[,1:3], interaction(Plastic[,c("rate", "additive")]))