learning R with swirl-vapply and tapply(不懂)

 上一章,我们学了apply家族里比较基础的两个函数:lapply()和sapply()。它们都是以一个列表作为输入,对列表中的每个元素采取某种函数操作。然后合并并返回结果。lapply()结果返回一个列表,而sapply()尝试简化这个列表。

learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)

本题选3,氮素不知道为什么!

learning R with swirl-vapply and tapply(不懂)

learning R with swirl-vapply and tapply(不懂)

本题选5,也不知道为什么!!!!!

learning R with swirl-vapply and tapply(不懂)