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#' @title Scale numeric variables in a data frame
#'
#' @description Applies `base::scale()` to numeric, integer, or
#' logical columns in a data frame. Non-numeric columns are left
#' unchanged.
#' @concept data_handling
#' @param x A data frame or matrix.
#' @param center Logical; if TRUE, center the variables.
#' @param scale Logical; if TRUE, scale the variables.
#'
#' @details
#' If `x` is not a data frame, `base::scale()` is applied directly.
#'
#' @return An object of the same class as `x`.
#'
#' @examples
#' scale_df(iris)
#'
#' @name scale_df
#' @export
scale_df <- function(x, center = TRUE, scale = TRUE){
if (!is(x, "data.frame")){
return(scale(x, center=center, scale=scale))
} else { ## x is dataframe
b <- sapply(x,
function(z){is(z, c("numeric")) || is(z, c("integer")) || is(z, c("logical")) })
if (!any(b)){ ## x only has numeric values
return(scale(x, center=center, scale=scale))
} else { ## x is dataframe with non-numerics
x2 <- x[,b, drop=FALSE]
x2 <- scale(x2, center=center, scale=scale)
x[, b] <- x2
if (!is.null(a <- attributes(x2)$"scaled:center"))
attr(x, "scaled:center") <- a
if (!is.null(a <- attributes(x2)$"scaled:scale"))
attr(x, "scaled:scale") <- a
return(x)
}
}
}
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