Calculate column deviations from central values

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, ...)

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.
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.
...: Arguments passed down

Value

A numeric matrix containing the deviations from the centering function.

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.

Author

Michael Friendly

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))

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