R提取数据帧中每个因子的最后一行值

Question

我有一个数据框，其中一列包含一系列可变长度的因子和包含值的其他列。如何只提取每个因子的最后一行值？

df <- data.frame(x=c("a","a","a","a","b","b","c","c","c","c","c","d","d","d","e","f","f","f","f","g","g"),y=c(diffinv(rnorm(20))),z=c(diffinv(rnorm(20))))
df

感谢您的帮助。

Answer 1

有很多选择。这不是最有效的，但它不需要包：

aggregate(. ~ x, df, tail, n = 1)