根据最近的时间戳在 R 中加入两个数据帧 [英] Join two data frames in R based on closest timestamp

问题描述

我有两个表(下面的表 1 和表 2)，我想根据最接近的时间戳将它们连接起来以形成 expected_output.如果可能的话，某种涉及 dplyr 的解决方案会很好，但如果它使事情进一步复杂化，那就不是了.

table1 =结构(列表(日期 = 结构(c(1437051300、1434773700、1431457200)), class = c("POSIXct", "POSIXt"), tzone = ""), val1 = c(94L,33L, 53L)), .Names = c("date", "val1"), row.names = c(NA, -3L), class = "data.frame")表 2 =结构(列表(日期 = 结构(c(1430248288、1435690482、1434050843)), class = c("POSIXct", "POSIXt"), tzone = ""), val2 = c(67L,90L, 18L)), .Names = c("date", "val2"), row.names = c(NA, -3L), class = "data.frame")预期输出 =结构(列表(日期 = 结构(c(1437051300、1434773700、1431457200)), class = c("POSIXct", "POSIXt"), tzone = ""), val1 = c(94L,33L, 53L), val2 = c(90L, 18L, 67L)), .Names = c("date", "val1","val2"), row.names = c(NA, -3L), class = "data.frame")

解决方案

使用 data.table 的滚动连接功能和 roll = "nearest":

require(data.table) # v1.9.6+setDT(table1)[, val2 := setDT(table2)[table1, val2, on = "date", roll = "nearest"]]

这里，val2 列是通过对 date 列执行 join 和 roll = "nearest" 来创建的> 选项.对于table1$date的每一行，计算与table2$date最接近的匹配行，并提取对应行的val2.>

Hi I have two tables (table1 and table2 below) and would like to join them based on the closest timestamp to form expected_output. Some kind of solution involving dplyr would be great if possible, but not if it further complicates things.

table1 = 
structure(list(date = structure(c(1437051300, 1434773700, 1431457200
), class = c("POSIXct", "POSIXt"), tzone = ""), val1 = c(94L, 
33L, 53L)), .Names = c("date", "val1"), row.names = c(NA, -3L
), class = "data.frame")

table2 = 
structure(list(date = structure(c(1430248288, 1435690482, 1434050843
), class = c("POSIXct", "POSIXt"), tzone = ""), val2 = c(67L, 
90L, 18L)), .Names = c("date", "val2"), row.names = c(NA, -3L
), class = "data.frame")

expected_output = 
structure(list(date = structure(c(1437051300, 1434773700, 1431457200
), class = c("POSIXct", "POSIXt"), tzone = ""), val1 = c(94L,
33L, 53L), val2 = c(90L, 18L, 67L)), .Names = c("date", "val1", 
"val2"), row.names = c(NA, -3L), class = "data.frame")

解决方案

Using rolling joins feature of data.table with roll = "nearest":

require(data.table) # v1.9.6+
setDT(table1)[, val2 := setDT(table2)[table1, val2, on = "date", roll = "nearest"]]

Here, val2 column is created by performing a join on the column date with roll = "nearest" option. For each row of table1$date, the closest matching row from table2$date is computed, and val2 for corresponding row is extracted.

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