scale_traits(df, method, cols)

Standardise trait columns: z-score ('zscore'), 0-1 range ('minmax'), or unit-variance without centering ('unit'). Returns data frame with scaled values.

utilitypreprocessing

Args:df — species × traitsmethod="zscore"cols — trait columns (default: all numeric)

scale_traits <- function(df, method = "zscore", cols = NULL) {
  if (is.null(cols)) cols <- names(df)[sapply(df, is.numeric)]
  
  scale_fn <- switch(method,
    zscore = function(x) (x - mean(x, na.rm=TRUE)) / sd(x, na.rm=TRUE),
    minmax = function(x) {
      r <- range(x, na.rm = TRUE)
      (x - r[1]) / (r[2] - r[1])
    },
    unit   = function(x) x / sd(x, na.rm = TRUE),
    stop("method must be 'zscore', 'minmax', or 'unit'")
  )
  
  df[, cols] <- lapply(df[, cols, drop = FALSE], scale_fn)
  df
}

# Example
scaled <- scale_traits(iris, method = "zscore")
apply(scaled[, 1:4], 2, mean)  # should be ~0