[英]R merge two dataframes by closest date
I have two large dataframes, dfA
and dfB
, for which I have generated simple examples here我有两个大数据
dfA
, dfA
和dfB
,我在这里生成了简单的例子
dfA = data.frame(id=c("Apple", "Banana", "Carrot", "Dates", "Egg"),
Answer_Date=as.Date(c("2013-12-07", "2014-12-07", "2015-12-07", "2016-12-07", "2017-12-07" )),
x1 = c(1, 2, 3, 4, 5),
x2 = c(10, 20, 30, 40, 50))
Browse[2]> dfA
id Answer_Date x1 x2
1 Apple 2013-12-07 1 10
2 Banana 2014-12-07 2 20
3 Carrot 2015-12-07 3 30
4 Dates 2016-12-07 4 40
5 Egg 2017-12-07 5 50
dfB = data.frame(id=c("Apple", "Apple", "Banana", "Banana", "Banana"),
Answer_Date=as.Date(c("2013-12-05", "2014-12-07", "2015-12-10", "2018-11-07", "2019-11-07" )),
x3 = c(5, 4, 3, 2, 1),
x4 = c(50, 40, 30, 20, 10))
Browse[2]> dfB
id Answer_Date x3 x4
1 Apple 2013-12-05 5 50
2 Apple 2014-12-07 4 40
3 Banana 2014-12-10 3 30
4 Banana 2018-11-07 2 20
5 Banana 2019-11-07 1 10
I'd like to merge them by the closest date so that I get the items that exist in both dfA and dfB matched exactly by id and as closely as possible by Answer_Date (ie minimum absolute value of date difference between the two dates).我想按最近的日期合并它们,以便我得到 dfA 和 dfB 中存在的项目,它们与 id完全匹配,并尽可能与 Answer_Date 匹配(即两个日期之间日期差异的最小绝对值)。 In this case I'd like to get
在这种情况下,我想得到
dfC
id Answer_Date.x Answer_Date.y x1 x2 x3 x4
1 Apple 2013-12-07 2013-12-05 1 10 5 50
2 Banana 2014-12-07 2014-12-10 2 20 3 30
Unfortunately struggling with merge() and trying out various solutions that I have found on StackOverflow hasn't solved my problem and has only got me confused.不幸的是,与 merge() 苦苦挣扎并尝试了我在 StackOverflow 上找到的各种解决方案并没有解决我的问题,只会让我感到困惑。 Would someone kindly point me to the right solution, ideally with a simple explanation as to why it works?
有人会为我指出正确的解决方案,最好是简单解释一下它为什么起作用吗?
Sincerely and with many thanks in advance真诚地,非常感谢
Thomas Philips托马斯·菲利普斯
Left join dfB
to dfA
, take the difference between dates per row and choose the smallest diff per id.左连接
dfB
到dfA
,取每行日期之间的差异并选择每个 id 的最小差异。
left_join(dfA, dfB, by = "id") %>%
mutate(date_diff = abs(Answer_Date.x - Answer_Date.y)) %>%
group_by(id) %>%
filter(date_diff == min(date_diff)) %>%
select(id, Answer_Date.x, Answer_Date.y, starts_with("x"), date_diff)
Then output is:然后输出是:
# A tibble: 2 x 8
# Groups: id [2]
id Answer_Date.x Answer_Date.y x1 x2 x3 x4 date_diff
<fct> <date> <date> <dbl> <dbl> <dbl> <dbl> <drtn>
1 Apple 2013-12-07 2013-12-05 1 10 5 50 2 days
2 Banana 2014-12-07 2014-12-10 2 20 3 30 3 days
By the way, in your sample code the third Answer_Date
in the definition of dfB
should be "2014-12-10"
instead of "2015-12-10"
.顺便说一下,在您的示例代码中,
Answer_Date
定义中的第三个dfB
应该是"2014-12-10"
而不是"2015-12-10"
。
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