获取与日期 'Around' 7 天前关联的分数

Question

这就是我的数据框的样子。最右边（第 4）列是我想要的列。对于一个给定的名字，我试图从 7 天前得出该人的分数。如果 7 天前没有确切的日期，那么我想要与最接近的日期（一行的日期 - 7 天）关联的分数。

library(data.table)
 dt <- fread('
    Name      Score     Date         ScoreAround7DaysAgo
    John       9       2016-01-01       NA
    John       6       2016-01-10       9
    John       3       2016-01-17       6
    John       5       2016-01-18       6
    Tom        9       2016-01-01       NA
    Tom        6       2016-01-10       9
    Tom        3       2016-01-17       6
    Tom        5       2016-01-18       6
                                ')
dt[, Date := as.IDate(Date)]

我试过dt[dt,roll=7+nearest]没用。谢谢你的帮助。

Answer 1

这个有效：

dt[, DateLag := Date - 7L ]
w = dt[dt, which = TRUE, on = c("Name", Date = "DateLag"), roll = "nearest"]

dt[ , `:=`(ScoreLag = Score[replace(w, w == .I, NA_integer_)], DateLag = NULL)]


   Name Score       Date ScoreAround7DaysAgo ScoreLag
1: John     9 2016-01-01                  NA       NA
2: John     6 2016-01-10                   9        9
3: John     3 2016-01-17                   6        6
4: John     5 2016-01-18                   6        6
5:  Tom     9 2016-01-01                  NA       NA
6:  Tom     6 2016-01-10                   9        9
7:  Tom     3 2016-01-17                   6        6
8:  Tom     5 2016-01-18                   6        6

它找到最接近 Date-7 的日期，但如果再次 Date 相同则丢弃它。

Answer 2

dt[, val := .SD[.(Name = Name, Date = Date - 7), on = c('Name', 'Date'), roll = 'nearest',
                c(NA, tail(Score, -1)), by = Name]$V1]
dt
#   Name Score       Date ScoreAround7DaysAgo val
#1: John     9 2016-01-01                  NA  NA
#2: John     6 2016-01-10                   9   9
#3: John     3 2016-01-17                   6   6
#4: John     5 2016-01-18                   6   6
#5:  Tom     9 2016-01-01                  NA  NA
#6:  Tom     6 2016-01-10                   9   9
#7:  Tom     3 2016-01-17                   6   6
#8:  Tom     5 2016-01-18                   6   6

获取与日期 'Around' 7 天前关联的分数

Fetching a score associated with a date 'Around' 7 days ago

r

zoo

dplyr

data.table