Move outcome to last column
Examples
ir <- set_outcome(iris, "Sepal.Length")
head(ir)
#> Sepal.Width Petal.Length Petal.Width Species Sepal.Length
#> 1 3.5 1.4 0.2 setosa 5.1
#> 2 3.0 1.4 0.2 setosa 4.9
#> 3 3.2 1.3 0.2 setosa 4.7
#> 4 3.1 1.5 0.2 setosa 4.6
#> 5 3.6 1.4 0.2 setosa 5.0
#> 6 3.9 1.7 0.4 setosa 5.4