How to substitute a special character between words in R [duplicate]

问题

I have a string of characters.

str = c(".wow", "if.", "not.confident", "wonder", "have.difficulty", "shower")

I am trying to replace "." in between words with a whitespace. So it would look like this

".wow", "if.", "not confident", "wonder", "have difficulty", "shower"

First, I tried

gsub("[\\w.\\w]", " ", str)
[1] "  o "            "if"              "not confident"   " onder"         
[5] "have difficulty" "sho er "

It gave me the whitespace I want, but chopped off all the w's. Then, I tried

gsub("\\w\\.\\w", " ", str)
[1] ".wow"          "if"            "no onfident"   "wonder"       
[5] "hav ifficulty" "shower."

It kept the w's, but brought away other characters right before and after ".".

I cannot use this either

gsub("\\.", " ", str)
[1] " wow"             "if "              "not.confident"   "wonder"         
[5] "have.difficulty" "shower"

because it will take away "." not in between words.

回答1:

Try

gsub('(\\w)\\.(\\w)', '\\1 \\2', str)
#[1] ".wow"            "if."             "not confident"   "wonder"         
#[5] "have difficulty" "shower"

gsub('(?<=[^.])[.](?=[^.])', ' ', str, perl=TRUE)

Or as @rawr suggested

gsub('\\b\\.\\b', ' ', str, perl = TRUE)

回答2:

Using capturing groups and back-references:

sub('(\\w)\\.(\\w)', '\\1 \\2', str)
# [1] ".wow"            "if."             "not confident"   "wonder"         
# [5] "have difficulty" "shower"

A capturing group can be created by placing the characters to be grouped inside a set of parenthesis ( ... ). Backreferences recall what was matched by a capturing group.

A backreference is specified as (\); followed by a digit indicating the number of the group.

Using lookaround assertions:

Lookarounds are zero-width assertions. They don't "consume" any characters on the string.

sub('(?<=\\w)\\.(?=\\w)', ' ', str, perl = TRUE)

来源：https://stackoverflow.com/questions/29476002/how-to-substitute-a-special-character-between-words-in-r

标签

regex

substitution