R等价于.first或.last sas运算符

Question

有人知道什么是SAS的最佳R替代品.或者持续.运营商？我没找到.

SAS拥有第一名.最后.自动变量,用于识别具有特定变量的相同值的组中的第一个和最后一个记录; 所以在以下数据集中定义了FIRST.model和LAST.model:

Model,SaleID,First.Model,Last.Model
Explorer,1,1,0
Explorer,2,0,0
Explorer,3,0,0
Explorer,4,0,1
Civic,5,1,0
Civic,6,0,0
Civic,7,0,1

Answer 1

这听起来像你正在寻找!duplicated,fromLast论证是FALSE或TRUE.

d <- datasets::Puromycin

d$state
# [1] treated   treated   treated   treated   treated   treated   treated  
# [8] treated   treated   treated   treated   treated   untreated untreated
#[15] untreated untreated untreated untreated untreated untreated untreated
#[22] untreated untreated
#Levels: treated untreated
!duplicated(d$state)
# [1]  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
#[13]  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
!duplicated(d$state,fromLast=TRUE)
# [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE
#[13] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE

此函数有一些警告和边缘情况行为,您可以通过帮助文件(?duplicated)找到它们.