干杯，我有两个具有以下结构的数据帧。
DF1:
Airlines HeadQ Date Cost_Index
American PHX 07-31-2016 220
American ATL 08-31-2016 150
American ATL 10-31-2016 150
Delta ATL 10-31-2016 180
American ATL 08-31-2017 200
第二数据帧DF2具有以下结构：
DF2:
Airlines HeadQ Date
American ATL 09-30-2016
Delta ATL 03-31-2017
现在查找数据帧DF1和DF2，我想将DF1更改为以下数据帧。
DF1:
Airlines HeadQ Date Cost_Index
American PHX 07-31-2016 220
American ATL 08-31-2016 0
American ATL 10-31-2016 150
Delta ATL 10-31-2016 180
American ATL 08-31-2017 200
条件是，从DF2查找DF1的Airlines和HeadQ，如果DF1 $ Date <DF2 $ Date，则将Cost_Index设置为0，否则继续使用Cost_Index。
我尝试了以下操作，但均未成功：
DF1$Cost_Index <- ifelse(DF1$Airlines == DF2$Airlines & DF1$HeadQ == DF2$HeadQ
& DF1$Date < DF2$Date, 0, DF1$Cost_Index)
Warning:
1: In DF1$Airlines == DF2$Airlines : longer object
length is not a multiple of shorter object length".
2: In<=.default(DF1$Date, DF2$Date) : longer object length is not a
multiple of shorter object length
DF1:
Airlines HeadQ Date Cost_Index
American PHX 07-31-2016 220
American ATL 08-31-2016 0
American ATL 10-31-2016 0
Delta ATL 10-31-2016 0
American ATL 08-31-2017 200
谁能指出我正确的方向？
笔记：
str(DF1$Date): Date, format: "2016-10-31"
str(DF2$Date): Date, format: "2016-08-31"
你可以做一个左连接的DF1，并DF2在Airlines与HeadQ列，然后更改的价值Cost_Index基础上，如果Date.x（从日DF1）小于Date.y（日期从DF2）。随着dplyr语法（如果额外的检查Date.y是NA按照你的逻辑，如果有在DF2不匹配，则应用于此Cost_Index应保持不变）：
library(dplyr)
# convert the Date column to Date class for comparison
df1$Date <- as.Date(df1$Date, "%m-%d-%Y")
df2$Date <- as.Date(df2$Date, "%m-%d-%Y")
df1 %>%
left_join(df2, by = c("Airlines", "HeadQ")) %>%
mutate(Cost_Index = ifelse(Date.x < Date.y & !is.na(Date.y), 0, Cost_Index),
Date = Date.x) %>%
select(-Date.x, -Date.y)
# Airlines HeadQ Cost_Index Date
# 1 American PHX 220 2016-07-31
# 2 American ATL 0 2016-08-31
# 3 American ATL 150 2016-10-31
# 4 Delta ATL 180 2016-10-31
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我来说两句