使用正则表达式从文件中提取文本的一部分

I am trying to use the following code:

我想使用以下代码：

x <- scan("myfile.txt", what="", sep="\n")

b <- grep('/^one/(.*?)/^four/', x, ignore.case = TRUE, perl = TRUE, value = TRUE,
     fixed = FALSE, useBytes = FALSE, invert = FALSE)

to extract a porting of text from myfile.txt

从myfile.txt中提取文本的移植

zero
one
two
three
four
five

the output I'm expecting is

我期待的输出是

one
two
three
four

I want to include the "one" and "four" I don't want to ditch them :)

我想包括“一”和“四”我不想抛弃他们:)

But somehow the regex is not working, The console output is giving no error but no text either... ?

但不知何故，正则表达式不起作用，控制台输出没有错误，但没有文字......？

I am using print(b)

我正在使用print（b）

2 个解决方案

#1

I'm not quite clear on what you're looking for, but just for fun...

我不太清楚你在寻找什么，但只是为了好玩......

R> x
[1] "zero"  "one"   "two"   "three" "four"  "five" 

R> grep("one|four", x) # get the position of "one" and "four"
[1] 2 5

Subset x to only include the things between "one" and "four"

子集x只包含“一”和“四”之间的东西

R> x[do.call(seq, as.list(grep("one|four", x)))]
[1] "one"   "two"   "three" "four"

#2

gsub('one(.*)four','\\1',paste(x,collapse=''))
[1] "zerotwothreefive"

or to get space between words :

或者在单词之间留出空格：

gsub('one(.*)four','\\1',paste(dat,collapse=' '))
[1] "zero  two three  five"

Edit after Gsee comment:

Gsee评论后编辑：

 gsub('.*(one.*four).*','\\1',paste(dat,collapse=' '))
[1] "one two three four"

But I think here no need to use regular expression :

但我认为这里不需要使用正则表达式：

 dat[seq(which(dat == 'one'),which(dat == 'four'))]
[1] "one"   "two"   "three" "four"

of course you can use min if the previous index in which are not in the good order.

当然，如果之前的索引不是正常的顺序，你可以使用min。

#1