[英]Using dplyr to filter all rows from one variable until another
我的数据如下所示:
data <- data.frame(
value = runif(10)
id = c("junk","start","1","2","end","morejunk","junk","start","4","end")
)
我想使用filter()
从id
"start"
到id
"end"
提取所有内容。 问题是开始行和结束行之间的观察次数不同,因此我无法筛选每x行。 有没有一种方法可以我可以from = "start"
until = "end"
来指定使用filter()
?
您可以首先确定“开始”和“结束”的位置。 然后使用这些成对的索引来索引data.frame。 假设每次都有对应的开始和结束对。
set.seed(0L)
data <- data.frame(
value = runif(10),
id = c("junk","start","1","2","end","morejunk","junk","start","4","end")
)
idx <- which(data$id %in% c("start", "end"))
lapply(split(idx, ceiling(seq_along(idx)/2)), function(x) data[x[1]:x[2],])
您可以
which
来标识带有"start"
和"end"
行索引, Map
将这些序列传递给:
unlist
列表可将列表简化为向量,并且 slice
子集 离开
library(dplyr)
set.seed(47)
data <- data.frame(
value = runif(10),
id = c("junk","start","1","2","end","morejunk","junk","start","4","end")
)
data %>% slice(unlist(Map(`:`,
which(.$id == 'start') + 1,
which(.$id == 'end') - 1)))
#> # A tibble: 3 × 2
#> value id
#> <dbl> <fctr>
#> 1 0.7615020 1
#> 2 0.8224916 2
#> 3 0.5433097 4
或在基地
data[unlist(Map(`:`,
which(data$id == 'start') + 1,
which(data$id == 'end') - 1)), ]
#> value id
#> 3 0.7615020 1
#> 4 0.8224916 2
#> 9 0.5433097 4
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