data("Groceries")
## add a complement-items for "whole milk" and "other vegetables"
g2 <- addComplement(Groceries, c("whole milk", "other vegetables"))
inspect(head(g2, 3))
## use a custom label for the complement-item
g2 <- addComplement(g2, "coffee", "NO coffee")
inspect(head(g2, 3))
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