test_let <- function() {
d <- data.frame(
Sepal_Length = c(5.8, 5.7),
Sepal_Width = c(4.0, 4.4),
Species = 'setosa',
rank = c(1, 2)
)
mapping = list(RankColumn = 'rank', GroupColumn = 'Species')
let(alias = mapping,
expr = {
# Notice code here can be written in terms of known or concrete
# names "RankColumn" and "GroupColumn", but executes as if we
# had written mapping specified columns "rank" and "Species".
# restart ranks at zero.
dres <- d
dres$RankColumn <- dres$RankColumn - 1
})
expect_equal(dres$rank, c(0,1))
invisible(NULL)
}
test_let()
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