R strsplit doesn't split on "."?

Question

I am writing an R script and want to define a variable to be used in plot annotations as part of the file name. I thought I would use the strsplit() function. Here is my code and the output:

infile = "ACC_1346.table.txt"

x = strsplit(infile, ".")

class(infile)
[1] "character"

class(x)
[1] "list"

str(x)
List of 1
$ : chr [1:18] "" "" "" "" ...

x[[1]]
[1] "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" "" ""

I expected the final output to be:

[1] "ACC_1346" "table" "txt"

What is going on here?

`?strsplit` then look at the examples. They recommend splitting on `[.]`. — Sam Dickson, Dec 17 '15 at 19:53
`cat(example(strsplit, give.lines = TRUE)[16:21], sep = "\n")` is your answer. — Rich Scriven, Dec 17 '15 at 20:12

score 7 · Accepted Answer · answered Dec 17 '15 at 19:57

7

To avoid regex altogether use fixed = TRUE in the call of strsplit

infile = "ACC_1346.table.txt"
x = strsplit(infile, ".", fixed = TRUE)

x

[[1]]
[1] "ACC_1346" "table" "txt"

answered Dec 17 '15 at 19:57

Andrey Shabalin

4,389
1
19
18

1

Worth noting that this is also more efficient than doing `\\.`. – Rich Scriven Dec 17 '15 at 20:08

OganM · Answer 2 · 2018-04-09T22:40:16.170

5

strsplit seeks for a regex to do it's splitting. In regex a "." is a wildcard that pretty much matches anything. To actually match the dot you need to escape using \. Since \ is also an escape character in R, you need to escape it twice as \\.

edited Apr 09 '18 at 22:40

answered Dec 17 '15 at 19:53

OganM

2,543
16
33

R strsplit doesn't split on "."?

2 Answers2