center_by centers and/or standardized a numeric vector by group. This
is sometimes called group-mean centering and/or group-SD standardizing.
list of atomic vector(s) and/or factor(s) (e.g., data.frame)
containing the groups. They should each have same length as
logical vector with length 1 specifying whether group-mean centering should be done.
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
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
1 2 3 4 5 6 7 8
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
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