R：gsub 固定=T 或 F 和特殊情况

Question

基于我之前提出的两个问题：

R: How to prevent memory overflow when using mgsub in vector mode?

gsub speed vs pattern length

我确实喜欢 @Tyler 关于使用 fixed=TRUE 的建议，因为它显着加快了计算速度。但是，它并不总是适用。我需要将caps 替换为一个独立的单词，不带或不带标点符号。先验不知道可以在单词之后或之前做什么，但它必须是任何常规标点符号（，。！ - + 等）。它不能是数字或字母。下面的例子。 capsule 必须保持原样。

i = "Here is the capsule, caps key, and two caps, or two caps. or even three caps-"          

orig = "caps"
change = "cap"

gsub_FixedTrue <- function(i) {
  i = paste0(" ", i, " ")
  orig = paste0(" ", orig, " ")
  change = paste0(" ", change, " ")

  i = gsub(orig,change,i,fixed=TRUE)
  i = gsub("^\\s|\\s$", "", i, perl=TRUE)

  return(i)
}

#Second fastest, doesn't clog memory
gsub_FixedFalse <- function(i) {

  i = gsub(paste0("\\b",orig,"\\b"),change,i)

  return(i)
}

print(gsub_FixedTrue(i)) #wrong
print(gsub_FixedFalse(i)) #correct

结果。需要第二个输出

[1] "Here is the capsule, cap key, and two caps, or two caps. or even three caps-"
[1] "Here is the capsule, cap key, and two cap, or two cap. or even three cap-"

Answer 1

使用您之前问题中的部分进行测试，我认为我们可以在标点符号前面放置一个占位符，如下所示，而不会太慢：

line <- c("one", "two one", "four phones", "and a capsule", "But here's a caps key",
    "Here is the capsule, caps key, and two caps, or two caps. or even three caps-" )
e <- c("one", "two", "caps")
r <- c("ONE", "TWO", "cap")


line <- rep(line, 1700000/length(line))

line <- gsub("([[:punct:]])", " <DEL>\\1<DEL> ", line, perl=TRUE)

## Start    
line2 <- paste0(" ", line, " ")
e2 <-  paste0(" ", e, " ")
r2 <- paste0(" ", r, " ")


for (i in seq_along(e2)) {
    line2 <- gsub(e2[i], r2[i], line2, fixed=TRUE)
}

gsub("^\\s|\\s$| <DEL>|<DEL> ", "", line2, perl=TRUE)