Question

具有这样的数据框：

dframe <- structure(list(id = c(1L, 1L, 1L, 1L, 2L, 2L, 2L), name = c("Google", 
    "Google", "Yahoo", "Amazon", "Amazon", "Google", "Amazon"), date = c("2008-11-01", 
    "2008-11-02", "2008-11-01", "2008-11-04", "2008-11-01", "2008-11-02", 
    "2008-11-03")), class = "data.frame", row.names = c(NA, -7L))

还有一个名字列表

list <- c("Google", "Yahoo", "Amazon")

如何获得这样的输出：

id   name       date
1 Google 2008-11-01
1  Yahoo 2008-11-01
1 Amazon 2008-11-04
2 Amazon 2008-11-01
2 Google 2008-11-02

对于每个ID，请从列表中保留第一个日期。我尝试了这个：

library(data.table)
library(tidyverse)
library(reshape2)
library(zoo)
date_list_first= dframe[,head(.SD,1), by = .(id)]

Answer 1

使用data.table的方法如下：

library(data.table)
setDT(dframe)
date_list_first = dframe[order(date)][!duplicated(id,by=c('name','id'))]

保留特定列表的第一个时间戳

1 个答案: