body = c(20,40,60,30,50)
beak = c(NA,4,6,3,1)
habitat = c("A", "B", "C", "A", "B")
trait = data.frame(body, beak, habitat)
standard(trait)
standard(trait, method = "iqr")
standard(trait, method = "range")
standard(trait, method = "rank")
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