I have this code:
> head(row.names(django_c1))
[1] "10" "16" "25" "26" "28" "48"
> row.names(django_c1) <- gsub("\"", "", row.names(django_c1))
> head(row.names(django_c1))
[1] "10" "16" "25" "26" "28" "48"
What I am trying to do is to delete all the quotation marks ("), however, it doesn't seem to work.
I have also tried:
row.names(django_c1) <- as.numeric(row.names(django_c1))
and:
row.names(django_c1) <- gsub(""", "", row.names(django_c1))
But none of these seem to work either. How can I delete the quotation marks?
You have this display because the result of rownames is a vector of character strings typeof()=="character", so R displays " around it to show that fact.
If you do head(django_c1) you won't see them.
Row and colum names are always character strings, if you want to access by arbitrary index, either use a list (but you will probably create issues since list[[2]]=0 automatically creates list[[1]]=NA) or use django_c1[str(custom_index),].
Precision : gsub('"', '', string) will perfectly remove " from your string if they are really part of your string, which means 'hey"' (displayed "hey\"") becomes 'hey' (displayed "hey"). The distinction must be clear between the content of the string and the way it is displayed.
Related
I haven't worked with regular expressions for quite some time, so I'm not sure if what I want to do can be done "directly" or if I have to work around.
My expressions look like the following two:
crb_gdp_g_100000_16_16_ftv_all.txt
crt_r_g_25000_20_40_flin_g_2.txt
Only the parts replaced by a asterisk are "varying", the other stuff is constant (or irrelevant, as in the case of the last part (after "f*_"):
cr*_*_g_*_*_*_f*_
Is there a straightfoward way to get only the values of the asterisk-parts? E.g. in case of "r" or "gdp" I have to include underscores, otherwise I get the r at the beginning of the expression. Including the underscores gives "r" or "gdp", but I only want "r" or "gdp".
Or in short: I know a lot about my expressions but I only want to extract the varying parts. (How) Can I do that?
You can use sub with captures and then strsplit to get a list of the separated elements:
str <- c("crb_gdp_g_100000_16_16_ftv_all.txt", "crt_r_g_25000_20_40_flin_g_2.txt")
strsplit(sub("cr([[:alnum:]]+)_([[:alnum:]]+)_g_([[:alnum:]]+)_([[:alnum:]]+)_([[:alnum:]]+)_f([[:alnum:]]+)_.+", "\\1.\\2.\\3.\\4.\\5.\\6", str), "\\.")
#[[1]]
#[1] "b" "gdp" "100000" "16" "16" "tv"
#[[2]]
#[1] "t" "r" "25000" "20" "40" "lin"
Note: I replaced \\w with [[:alnum:]] to avoid inclusion of the underscore.
We can also use regmatches and regexec to extract these values like this:
regmatches(str, regexec("^cr([^_]+)_([^_]+)_g_([^_]+)_([^_]+)_([^_]+)_f([^_]+)_.*$", str))
[[1]]
[1] "crb_gdp_g_100000_16_16_ftv_all.txt" "b"
[3] "gdp" "100000"
[5] "16" "16"
[7] "tv"
[[2]]
[1] "crt_r_g_25000_20_40_flin_g_2.txt" "t" "r"
[4] "25000" "20" "40"
[7] "lin"
Note that the first element in each vector is the full string, so to drop that, we can use lapply and "["
lapply(regmatches(str,
regexec("^cr([^_]+)_([^_]+)_g_([^_]+)_([^_]+)_([^_]+)_f([^_]+)_.*$", str)),
"[", -1)
[[1]]
[1] "b" "gdp" "100000" "16" "16" "tv"
[[2]]
[1] "t" "r" "25000" "20" "40" "lin"
I'm trying to split a string in R using strsplit and a perl regex. The string consists of various alphanumeric tokens separated by periods or hyphens, e.g "WXYZ-AB-A4K7-01A-13B-J29Q-10". I want to split the string:
wherever a hyphen appears.
wherever a period appears.
between the second and third character of a token that is exactly 3 characters long and consists of 2 digits followed by 1 capital letter, e.g "01A" produces ["01", "A"] (but "012A", "B1A", "0A1", and "01A2" are not split).
For example, "WXYZ-AB-A4K7-01A-13B-J29Q-10" should produce ["WXYZ", "AB", "01", "A", "13", "B", "J29Q", "10"].
My current regex is ((?<=[-.]\\d{2})(?=[A-Z][-.]))|[.-] and it works perfectly in this online regex tester.
Furthermore, the two parts of the alternative, ((?<=[-.]\\d{2})(?=[A-Z][-.])) and [.-], both serve to split the string as intended in R, when they are used separately:
#correctly splits on periods and hyphens
strsplit("WXYZ-AB-A4K7-01A-13B-J29Q-10", "[.-]", perl=T)
[[1]]
[1] "WXYZ" "AB" "A4K7" "01A" "13B" "J29Q" "10"
#correctly splits tokens where a letter follows two digits
strsplit("WXYZ-AB-A4K7-01A-13B-J29Q-10", "((?<=[-.]\\d{2})(?=[A-Z][-.]))", perl=T)
[[1]]
[1] "WXYZ-AB-A4K7-01" "A-13" "B-J29Q-10"
But when I try and combine them using an alternative, the second regex stops working, and the string is only split on periods and hyphens:
#only second alternative is used
strsplit("WXYZ-AB-A4K7-01A-13B-J29Q-10", "((?<=[-.]\\d{2})(?=[A-Z][-.]))|[.-]", perl=T)
[[1]]
[1] "WXYZ" "AB" "A4K7" "01A" "13B" "J29Q" "10"
Why is this happening? Is it a problem with my regex, or with strsplit? How can I achieve the desired behavior?
Desired output:
## [[1]]
## [1] "WXYZ" "AB" "A4K7" "01" "A" "13" "B" "J29Q" "10"
An alternative that prevents you from having to consider how the strsplit algorithm works, is to use your original regex with gsub to insert a simple splitting character in all the right places, then do use strsplit to do the straightforward splitting.
strsplit(
gsub("((?<=[-.]\\d{2})(?=[A-Z][-.]))|[.-]", "-", x, perl = TRUE),
"-",
fixed = TRUE)
#[[1]]
#[1] "XYZ" "02" "01" "C" "33" "D" "2285"
Of course, RichScriven's answer and Wiktor Stribiżew's comment are probably better since they only have one function call.
You may use a consuming version of a positive lookahead (a match reset operator \K) to make sure strsplit works correctly in R and avoid the problem of using a negative lookbehind inside a positive one.
"(?<![^.-])\\d{2}\\K(?=[A-Z](?:[.-]|$))|[.-]"
See the R demo online (and a regex demo here).
strsplit("XYZ-02-01C-33D-2285", "(?<![^.-])\\d{2}\\K(?=[A-Z](?:[.-]|$))|[.-]", perl=TRUE)
## => [[1]]
## [1] "XYZ" "02" "01" "C" "33" "D" "2285"
strsplit("WXYZ-AB-A4K7-01A-13B-J29Q-10", "(?<![^.-])\\d{2}\\K(?=[A-Z](?:[.-]|$))|[.-]", perl=TRUE)
## => [[1]]
## [1] "WXYZ" "AB" "A4K7" "01" "A" "13" "B" "J29Q" "10"
Here, the pattern matches:
(?<![^.-])\d{2}\K(?=[A-Z](?:[.-]|$)) - a sequence of:
(?<![^.-])\d{2} - 2 digits (\d{2}) that are not preceded with a char other than . and - (i.e. that are preceded with . or - or start of string, it is a common trick to avoid alternation inside a lookaround)
\K - the match reset operator that makes the regex engine discard the text matched so far and go on matching the subsequent subpatterns if any
| - or
[.-] - matches . or -.
Thanks to Rich Scriven and Jota I was able to solve the problem. Every time strsplit finds a match, it removes the match and everything to its left before looking for the next match. This means that regex's that rely on lookbehinds may not function as expected when the lookbehind overlaps with a previous match. In my case, the hyphens between tokens were removed upon being matched, meaning that the second regex could not use them to detect the beginning of the token:
#first match found
"WXYZ-AB-A4K7-01A-13B-J29Q-10"
^
#match + left removed
"AB-A4K7-01A-13B-J29Q-10"
#further matches found and removed
"01A-13B-J29Q-10"
#second regex fails to match because of missing hyphen in lookbehind:
#((?<=[-.]\\d{2})(?=[A-Z][-.]))
# ^^^^^^^^
"01A-13B-J29Q-10"
#algorithm continues
"13B-J29Q-10"
This was fixed by replacing the [.-] class to detect the edges of the token in the lookbehind with a boundary anchor, as per Jota's suggestion:
> strsplit("WXYZ-AB-A4K7-01A-13B-J29Q-10", "[-.]|(?<=\\b\\d{2})(?=[A-Z]\\b)", perl=T)
[[1]]
[1] "WXYZ" "AB" "A4K7" "01" "A" "13" "B" "J29Q" "10"
I want to get all characters that are ahead of the first "." if there is one. Otherwise, I want to get back the same character ("8" -> "8").
Example:
v<-c("7.7.4","8","12.6","11.5.2.1")
I want to get something like this:
[1] "7 "8" "12" "11"
My idea was to split each element at "." and then only take the first split. I found no solution that worked...
You can use sub
sub("\\..*", "", v)
#[1] "7" "8" "12" "11"
or a few stringi options:
library(stringi)
stri_replace_first_regex(v, "\\..*", "")
#[1] "7" "8" "12" "11"
# extract vs. replace
stri_extract_first_regex(v, "[^\\.]+")
#[1] "7" "8" "12" "11"
If you want to use a splitting approach, these will work:
unlist(strsplit(v, "\\..*"))
#[1] "7" "8" "12" "11"
# stringi option
unlist(stri_split_regex(v, "\\..*", omit_empty=TRUE))
#[1] "7" "8" "12" "11"
unlist(stri_split_fixed(v, ".", n=1, tokens_only=TRUE))
unlist(stri_split_regex(v, "[^\\w]", n=1, tokens_only=TRUE))
Other sub variations that use a capture group to target the leading characters specifically:
sub("(\\w+).+", "\\1", v) # \w matches [[:alnum:]_] (i.e. alphanumerics and underscores)
sub("([[:alnum:]]+).+", "\\1", v) # exclude underscores
# variations on a theme
sub("(\\w+)\\..*", "\\1", v)
sub("(\\d+)\\..*", "\\1", v) # narrower: \d for digits specifically
sub("(.+)\\..*", "\\1", v) # broader: "." matches any single character
# stringi variation just for fun:
stri_extract_first_regex(v, "\\w+")
scan() would actually work well for this. Since we want everything before the first ., we can use that as a comment character and scan() will remove everything after and including that character, for each element in v.
scan(text = v, comment.char = ".")
# [1] 7 8 12 11
The above returns a numeric vector, which might be where you are headed. If you need to stick with characters, add the what argument to denote we want a character vector returned.
scan(text = v, comment.char = ".", what = "")
# [1] "7" "8" "12" "11"
Data:
v <- c("7.7.4", "8", "12.6", "11.5.2.1")
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?
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.
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"
Besides strsplit(), you can also use scan(). Try:
scan(what = "", text = s, sep = ".")
# Read 4 items
# [1] "I" "want" "to" "split"
> test = "23*45"
I'd like to split testby the symbol *
I tried...
> strsplit(test,'*')
and I got...
[[1]]
[1] "2" "3" "*" "4" "5"
What I aim to have is:
[[1]]
[1] "23" "45"
You need to escape the star...
test = "23*45"
strsplit( test , "\\*" )
#[[1]]
#[1] "23" "45"
The split is a regular expression and * means the preceeding item is matched zero or more times. You are splitting on nothing , i.e. splitting into individual characters, as noted in the Details section of strsplit(). \\* means *treat * as a literal *.
Alternatively use the fixed argument...
strsplit( test , "*" , fixed = TRUE )
#[[1]]
#[1] "23" "45"
Which gets R to treat the split pattern as literal and not a regular expression.
You might want to look at this package:
http://www.rexamine.com/resources/stringi/
To install this package simply run:
install.packages("stringi")
Example:
stri_split_fixed(test, "*")