如何根据位置的数值向量拆分字符向量

Question

我想根据用于拆分点的第二个数值向量将字符向量拆分为子字符串

vec <- "LAYRVCMTNEGHPWVSLVVQKTRLQISQDPSLNYEYLPTMGLKSFIQASLALLFGKHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHKDARIVYIISSQKELHGLVFQDMGFTVYEYSVWDPKKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM"
split.points <- c(25, 32, 55, 90, 124)

我想在 split.points 向量中给定的位置将上述字符向量切割成六个不同的子字符串。

听起来很简单，但我知道的 split 命令要么只适用于特定的正则表达式（模式），要么适用于一定长度的子字符串。

如有任何帮助，我将不胜感激。

Answer 1

我们可以使用 separate 来自 tidyr

library(tidyverse)
data_frame(vec) %>%
      separate(vec, into = paste0('vec', 1:6), sep = split.points) %>% 
      unlist(., use.names = FALSE)
#[1] "LAYRVCMTNEGHPWVSLVVQKTRLQ"                    "ISQDPSL"                                      "NYEYLPTMGLKSFIQASLALLFG"                     
#[4] "KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK"          "DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP"
#[6] "KKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM"

base R 选项将是 substr

unname(mapply(substr, vec, start = c(1, split.points+1), stop = c(split.points, nchar(vec))))
#[1] "LAYRVCMTNEGHPWVSLVVQKTRLQ"                    "ISQDPSL"                                      "NYEYLPTMGLKSFIQASLALLFG"                     
#[4] "KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK"          "DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP"           "KKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM"

Answer 2

我们可以试试substring:

substring(
    vec,
    c(1, split.points + 1),
    c(split.points, nchar(vec))
)
# [1] "LAYRVCMTNEGHPWVSLVVQKTRLQ"                    "ISQDPSL"                                     
# [3] "NYEYLPTMGLKSFIQASLALLFG"                      "KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK"         
# [5] "DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP"           "KKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM"

Answer 3

另一种选择是使用 read.fwf:

unlist(read.fwf(textConnection(vec), 
                widths = c(25, diff(split.points)), 
                as.is = TRUE), 
       use.names = FALSE)

给出：

[1] "LAYRVCMTNEGHPWVSLVVQKTRLQ"          
[2] "ISQDPSL"                            
[3] "NYEYLPTMGLKSFIQASLALLFG"            
[4] "KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK"
[5] "DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP"

当您的字符向量源自数据文件时，我不会感到惊讶。在那种情况下 read.fwf 会特别有用。一个例子：

vec2 <- "LAYRVCMTNEGHPWVSLVVQKTRLQISQDPSLNYEYLPTMGLKSFIQASLALLFGKHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHKDARIVYIISSQKELHGLVFQDMGFTVYEYSVWDPKKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM
LAYRVCMTNEGHPWVSLVVQKTRLQISQDPSLNYEYLPTMGLKSFIQASLALLFGKHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHKDARIVYIISSQKELHGLVFQDMGFTVYEYSVWDPKKLCMDPDILLNVVEQIPHGCVLVMGNIIDCKLTPSGWAKLMSM"

read.fwf(textConnection(vec2), 
         widths = c(25, diff(split.points)), 
         as.is=TRUE)

这将给出：

                         V1      V2                      V3                                  V4                                 V5
1 LAYRVCMTNEGHPWVSLVVQKTRLQ ISQDPSL NYEYLPTMGLKSFIQASLALLFG KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP
2 LAYRVCMTNEGHPWVSLVVQKTRLQ ISQDPSL NYEYLPTMGLKSFIQASLALLFG KHSQAIVENRVGGVHTVGDSGAFQLGVQFLRAWHK DARIVYIISSQKELHGLVFQDMGFTVYEYSVWDP

如何根据位置的数值向量拆分字符向量

How to split a character vector based on a numeric vector for positions

r

split

strsplit