How to use the strsplit function with a period

问题

I would like to split the following string by its periods. I tried strsplit() with \".\" in the split argument, but did not get the result I want.

s <- \"I.want.to.split\"
strsplit(s, \".\")
[[1]]
 [1] \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\" \"\"

The output I want is to split s into 4 elements in a list, as follows.

[[1]]
[1] \"I\"     \"want\"  \"to\"    \"split\"

What should I do?

回答1:

When using a regular expression in the split argument of strsplit(), you've got to escape the . with \\., or use a charclass [.]. Otherwise you use . as its special character meaning, "any single character".

s <- "I.want.to.split"
strsplit(s, "[.]")
# [[1]]
# [1] "I"     "want"  "to"    "split"

But the more efficient method here is to use the fixed argument in strsplit(). Using this argument will bypass the regex engine and search for an exact match of ".".

strsplit(s, ".", fixed = TRUE)
# [[1]]
# [1] "I"     "want"  "to"    "split"

And of course, you can see help(strsplit) for more.

回答2:

You need to either place the dot . inside of a character class or precede it with two backslashes to escape it since the dot is a character of special meaning in regex meaning "match any single character (except newline)"

s <- 'I.want.to.split'
strsplit(s, '\\.')
# [[1]]
# [1] "I"     "want"  "to"    "split"

回答3:

Besides strsplit(), you can also use scan(). Try:

scan(what = "", text = s, sep = ".")
# Read 4 items
# [1] "I"     "want"  "to"    "split"

来源：https://stackoverflow.com/questions/26665100/how-to-use-the-strsplit-function-with-a-period

标签

strsplit