R 仅保留数据框中与特定图案长度匹配的行

我有一个如下所示的数据框：

df <- structure(list(Sequence = c("Sequence", "Sequence", "Sequence", 
"Sequence", "Sequence", "Sequence", "Sequence", "Sequence", "Sequence", 
"Sequence", "Sequence", "Sequence", "Sequence", "Sequence", "Sequence", 
"Sequence", "Sequence", "Sequence", "Sequence", "Sequence", "Sequence", 
"Sequence", "Sequence", "Sequence", "Sequence"), start = c(1, 
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 
20, 21, 22, 23, 24, 25), end = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25), 
    score = c(-0.205, -0.229, -0.115, -0.427, -0.327, -0.543, 
    -0.717, -0.923, -1.241, -1.471, -1.737, -1.717, -1.247, -1.137, 
    -0.689, -0.731, -0.337, 0.091, 0.579, 0.93, 0.575, 0.128, 
    -0.036, -0.186, -0.259), residue = c("M", "D", "A", "R", 
    "M", "R", "E", "L", "S", "F", "K", "V", "V", "L", "L", "G", 
    "E", "G", "R", "V", "G", "K", "T", "S", "L"), epitope = c("E", 
    "E", "E", ".", ".", ".", ".", ".", "E", ".", ".", "E", "E", 
    ".", ".", ".", ".", ".", "E", "E", "E", "E", "E", "E", "."
    )), .Names = c("Sequence", "start", "end", "score", "residue", 
"epitope"), class = c("data.table", "data.frame"), row.names = c(NA, 
-25L))

---

我们可以使用

data.table

中的

rleid

。将“data.frame”转换为“data.table”（

setDT（df）

，按“表位”的游程长度id分组），创建一个逻辑向量（

.N>=5&表位==“E”

），提取行索引（

.I

）并对数据进行子集

library(data.table)
setDT(df)[df[, .I[.N >=5 & epitope == "E"], rleid(epitope)]$V1]
#     Sequence start end  score residue epitope
#1: Sequence    19  19  0.579       R       E
#2: Sequence    20  20  0.930       V       E
#3: Sequence    21  21  0.575       G       E
#4: Sequence    22  22  0.128       K       E
#5: Sequence    23  23 -0.036       T       E
#6: Sequence    24  24 -0.186       S       E

---

或者我们可以使用类似的方法，从

base R

df[inverse.rle(within.list(rl, values[!(lengths >=5 & values)] <- FALSE)),]

df[inverse.rle（在.list内（rl，值[！（长度>=5&值）]
df[inverse.rle(within.list(rl, values[!(lengths >=5 & values)] <- FALSE)),]