我们可以使用group by选项，然后执行 sample p>

We can use group by option and then do sample

dt[, NextItem := sample(x, 1), by = Name]

或者您也可以使用 .N 而不是 / code>

Or you can also do this with .N instead of by

dt[, NextItem := sample(x, .N, replace = TRUE)]