r语言 - 根据其他列data.table中值的相对大小创建新列

Question

我有一个表，其中两列的值在0到1之间。例如:

set.seed(123)
table <- data.table(value1 = runif(10),
value2 = runif(10))
table
value1     value2
0.2875775 0.95683335
0.7883051 0.45333416
0.4089769 0.67757064
0.8830174 0.57263340
0.9404673 0.10292468
0.0455565 0.89982497
0.5281055 0.24608773
0.8924190 0.04205953
0.5514350 0.32792072
0.4566147 0.95450365

我想使用数据。表创建一个新的二进制列，将value2和value1之间差异最大的x行赋值为1。我可以"有所作为"。像这样的列:

table[,difference:=value1-value2]

我可以用order和tail找到x最大的差异，例如，如果x是5:

x<-5
table[order(difference), tail(.SD, x)]

但是我还没能想出一种方法来将这些与ifelse或case_when之类的东西结合起来，将x最大的差异分配为1，将其余的分配为0。

Answer 1

setorderv(table, "difference", order = -1)
table[, large := 0]
x <- 5
table[1:x, large := 1]

Answer 2

我希望这能解决你的问题:

library(data.table)
library(dtplyr)
library(dplyr)
#> 
#> Attache Paket: 'dplyr'
#> The following objects are masked from 'package:data.table':
#> 
#>     between, first, last
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
set.seed(123)
table <- data.table(value1 = runif(10),
value2 = runif(10))
table
#>        value1     value2
#>  1: 0.2875775 0.95683335
#>  2: 0.7883051 0.45333416
#>  3: 0.4089769 0.67757064
#>  4: 0.8830174 0.57263340
#>  5: 0.9404673 0.10292468
#>  6: 0.0455565 0.89982497
#>  7: 0.5281055 0.24608773
#>  8: 0.8924190 0.04205953
#>  9: 0.5514350 0.32792072
#> 10: 0.4566147 0.95450365
x <- 5
table <- table %>% 
lazy_dt() %>% 
mutate(difference = value1 - value2) %>% 
arrange(desc(difference)) %>% 
mutate(difference = ifelse(test = row_number() <= x, yes = 1, no = 0)) %>% 
as.data.table()
table
#>        value1     value2 difference
#>  1: 0.8924190 0.04205953          1
#>  2: 0.9404673 0.10292468          1
#>  3: 0.7883051 0.45333416          1
#>  4: 0.8830174 0.57263340          1
#>  5: 0.5281055 0.24608773          1
#>  6: 0.5514350 0.32792072          0
#>  7: 0.4089769 0.67757064          0
#>  8: 0.4566147 0.95450365          0
#>  9: 0.2875775 0.95683335          0
#> 10: 0.0455565 0.89982497          0

问候,m .

^{由reprex包(v2.0.1)于20121-10-11创建}