center_by: Centering and/or Standardizing a Numeric Vector by Group
In quest: Prepare Questionnaire Data for Analysis

Description Usage Arguments Details Value See Also Examples

center_by centers and/or standardized a numeric vector by group. This is sometimes called group-mean centering and/or group-SD standardizing.

1	center_by(x, grp, center = TRUE, scale = FALSE)

`x`	numeric vector.
`grp`	list of atomic vector(s) and/or factor(s) (e.g., data.frame) containing the groups. They should each have same length as `x`. It can also be an atomic vector or factor, which will then be made the first element of a list internally.
`center`	logical vector with length 1 specifying whether group-mean centering should be done.
`scale`	logical vector with length 1 specifying whether group-SD scaling should be done.

center_by first coerces x to a matrix in preparation for the core of the function, which is essentially: lapply(X = split(x = x, f = grp), FUN = scale.default). If the coercion results in a non-numeric matrix (e.g., x is a character vector or factor), then an error is returned. An error is also returned if x and the elements of grp do not have the same length.

numeric vector of x centered and/or standardized by group with the same names as x.

centers_by center centers scale.default

chick_data <- as.data.frame(ChickWeight) # because the "groupedData" class calls
   # `[.groupedData`, which is different than `[.data.frame`
center_by(x = ChickWeight[["weight"]], grp = ChickWeight[["Chick"]])
center_by(x = setNames(obj = ChickWeight[["weight"]], nm = row.names(ChickWeight)),
   grp = ChickWeight[["Chick"]]) # with names
tmp_nm <- c("Type","Treatment") # b/c Roxygen2 doesn't like a c() within a []
center_by(x = as.data.frame(CO2)[["uptake"]], grp = as.data.frame(CO2)[tmp_nm],
   scale = TRUE) # multiple grouping vectors