如果x的时间戳在y的时间间隔内，则合并两个数据帧 [英] Merge two dataframes if timestamp of x is within time interval of y

问题描述

我无法解决此问题.我有两个数据框. DF1和DF2.如果DF1中的时间戳在DF2中指定的时间间隔内，我想将DF2的列合并到DF1中. 这是两个数据帧的示例:

I cannot get a solution to this problem. I have two dataframes. DF1 and DF2. I would like to merge the columns of DF2 to DF1 if the timestamp in DF1 is within the time interval specified in DF2. Here is an example of the two dataframes:

DF1 <- structure(list(Airspeed = c(582L, 478L, 524L), Outbound.Track = c(119L, 78L,134L), Rem.Ground.Dist = c(369L, 119L, 196L), Timestamp=structure(c(1451636817.52577, 1451638203.76569, 1451637753.43511),class = c("POSIXct", "POSIXt"), tzone = "")), .Names =c("Airspeed", "Outbound.Track","Rem.Ground.Dist", "Timestamp"), row.names =c(1L, 12L, 7L), class = c("data.table", "data.frame"))

DF2 <- structure(list(Temperature = c(-18.5, -60, -35), Wind_Direction = c("324", "335", "313"), Wind_Speed = c("032", "041", "056"), onebef =structure(c(1451629620, 1451634660, 1451637000), class = c("POSIXct", "POSIXt"), tzone = ""), oneaft = structure(c(1451636820, 1451641860, 1451644200), class =c("POSIXct", "POSIXt"))), .Names = c("Temperature", "Wind_Direction", "Wind_Speed","onebef", "oneaft"), row.names = c(1358L, 1654L, 2068L), class = "data.frame")

head(DF1)
head(DF2)

我想将DF1与DF2合并.因此，如果存在匹配项(DF1的时间戳在任何DF2的时间间隔内)，则应将DF2的值(Wind_Speed，Wind_Direction，Temperature)添加到DF1.

I want to merge DF1 with DF2. So if there is a match (timestamp of DF1 is within time interval of any DF2), the values of DF2 (Wind_Speed, Wind_Direction, Temperature) should be added to DF1.

我面临的两个问题:

1. 如何进行匹配/合并?我的数据框很大(DF1和DF2中有7000行)

1. How to do the match/merge? My dataframe is quite large (7000 rows in DF1 and DF2)

如果有多个匹配项，如何确保DF1的行重复?

How to ensure that rows of DF1 are duplicated if there are several matches?

期待您的帮助！谢谢

推荐答案

您可以使用sqldf:

You could use sqldf:

library(sqldf)
df<-sqldf('select d1.*,d2.*
           from DF1 d1
           left join DF2 d2
             on d1.Timestamp >= d2.onebef
               AND d1.Timestamp <= d2.oneaft
          ')
df

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