Let's say I want a Regex expression that will only match numbers between 18 and 31. What is the right way to do this?
I have a set of strings that look like this:
"quiz.18.player.total_score"
"quiz.19.player.total_score"
"quiz.20.player.total_score"
"quiz.21.player.total_score"
I am trying to match only the strings that contain the numbers 18-31, and am currently trying something like this
(quiz.)[1-3]{1}[1-9]{1}.player.total_score
This obviously won't work because it will actually match all numbers between 11-39. What is the right way to do this?
Regex: 1[89]|2\d|3[01]
For matching add additional text and escape the dots:
quiz\.(?:1[89]|2\d|3[01])\.player\.total_score
Details:
(?:) non-capturing group
[] match a single character present in the list
| or
\d matches a digit (equal to [0-9])
\. dot
. matches any character
!) If s is the character vector read the fields into a data frame picking off the second field and check whether it is in the desired range. Put the result in logical vector ok and get those elements from s. This uses no regular expressions and only base R.
digits <- read.table(text = s, sep = ".")$V2
s[digits %in% 18:31]
2) Another approach based on the pattern "\\D" matching any non-digit is to remove all such characters and then check if what is left is in the desired range:
digits <- gsub("\\D", "", s)
s[digits %in% 18:31]
2a) In the development version of R (to be 3.6.0) we could alternately use the new whitespace argument of trimws like this:
digits <- trimws(s, whitespace = "\\D")
s[digits %in% 18:31]
3) Another alternative is to simply construct the boundary strings and compare s to them. This will work only if all the number parts in s are exactly the same number of digits (which for the sample shown in the question is the case).
ok <- s >= "quiz.18.player.total_score" & s <= "quiz.31.player.total_score"
s[ok]
This is done using character ranges and alternations. For your range
3[10]|[2][0-9]|1[8-9]
Demo
Related
I wanted to extract certain words from a bigger word-list. One example of a desired extracted word-list is: extract all the words that contain /s/ followed by /r/. So this should give me words such as sər'ka:rəh, e:k'sa:r, səmʋitərəɳ, and so:'ha:rd. from the bigger word-list.
Consider the data (IPA transcription) to be the one given below:
sər'ka:rəh
sə'lᴔ:nija:
hã:ki:
pu:'dʒa:ẽ:
e:k'sa:r
mritko:
dʒʱã:sa:
pə'hũtʃ'ne:'ʋa:le:
kərəpʈ
tʃinhirit
tʃʰəʈʈʰi:
dʱũdʱ'la:pən
səmʋitərəɳ
so:'ha:rd
məl'ʈi:spe:'ʃijliʈi:
la:'pər'ʋa:i:
upləbɡʱ
Thanks much!
Here's an answer to the issue described in the first paragraph of your post. (To my mind, the examples in the second paragraph are inconsistent with the issue described in the first para, so I'll take the liberty of ignoring them here).
You say you want to "extract all the words that contain p followed by t". The word 'extract' implies that there are other characters in the same string than those you want to match and extract. The verb 'contain' implies that the words you want to extract need not necessarily have p in word-initial position. Based on these premises, here's some mock data and a solution to the task:
Data:
x <- c("pastry is to the pastor's appetite what pot is to the pupil's")
Solution:
libary(stringr)
unlist(str_extract_all(x, "\\b\\w*(?<=p)\\w*t\\w*\\b"))
This uses word boundaries \\b to extract the target words from the surrounding context; it further uses positive lookbehind (?<=...) to assert the condition that for there to be a matching t there needs to be a p character occurring prior to the match.
The regex in more detail:
\\b: the opening word boundary
\\w*: zero or more alphanumeric chars (or an underscore)
(?<=p): positive lookbehind: "if and only if you see a p char on
the left..."
\\w*: zero or more alphanumeric chars (or an underscore)
t: the literal character t
\\w*: zero or more alphanumeric chars (or an underscore)
\\b: the closing word boundary
Result:
[1] "pastry" "pastor" "appetite" "pot"
EDIT 1:
Now that the question has been updated, a more definitive answer is possible.
Data:
x <- c("sər'ka:rəh","sə'lᴔ:nija:","hã:ki:","pu:'dʒa:ẽ:","e:k'sa:r",
"mritko:","dʒʱã:sa:","pə'hũtʃ'ne:'ʋa:le:","kərəpʈ","tʃinhirit",
"tʃʰəʈʈʰi:","dʱũdʱ'la:pən","səmʋitərəɳ","so:'ha:rd",
"məl'ʈi:spe:'ʃijliʈi:", "la:'pər'ʋa:i:","upləbɡʱ")
If you want to match (rather than extract) words that "contain /s/ followed by /r/", you can use grepin various ways. Here are two ways:
grep("s.*r", x, value = T)
or:
grep("(?<=s).*r", x, value = T, perl = T) # with lookbehind
The result is the same in either case:
[1] "sər'ka:rəh" "e:k'sa:r" "səmʋitərəɳ" "so:'ha:rd"
EDIT 2:
If the aim is to match words that "contain /s/ or /p/ followed by /r/ or /t/", you can use the metacharacter | to allow for alternatives:
grep("s.*r|s.*t|p.*r|p.*t", x, value = T)
# or, more succinctly:
grep("(s|p).*(r|t)", x, value = T)
[1] "sər'ka:rəh" "e:k'sa:r" "pə'hũtʃ'ne:'ʋa:le:" "səmʋitərəɳ" "so:'ha:rd"
[6] "la:'pər'ʋa:i:"
You can use grep function. Assuming your list is called list:
grep("p[a-z]+t", list, value=TRUE)
How can I extract digits from a string that can have a structure of xxxx.x or xxxx.x-x and combine them as a number? e.g.
list <- c("1010.1-1", "1010.2-1", "1010.3-1", "1030-1", "1040-1",
"1060.1-1", "1060.2-1", "1070-1", "1100.1-1", "1100.2-1")
The desired (numeric) output would be:
101011, 101021, 101031...
I tried
regexp <- "([[:digit:]]+)"
solution <- str_extract(list, regexp)
However that only extracts the first set of digits; and using something like
regexp <- "([[:digit:]]+\\.[[:digit:]]+\\-[[:digit:]]+)"
returns the first result (data in its initial form) if matched otherwise NA for shorter strings. Thoughts?
Remove all non-digit symbols:
list <- c("1010.1-1", "1010.2-1", "1010.3-1", "1030-1", "1040-1", "1060.1-1", "1060.2-1", "1070-1", "1100.1-1", "1100.2-1")
as.numeric(gsub("\\D+", "", list))
## => [1] 101011 101021 101031 10301 10401 106011 106021 10701 110011 110021
See the R demo online
I have no experience with R but I do know regular expressions. When I look at the pattern you're specifying "([[:digit:]]+)". I assume [[:digit:]] stands for [0-9], so you're capturing one group of digits.
It seems to me you're missing a + to make it capture multiple groups of digits.
I'd think you'd need to use "([[:digit:]]+)+".
I need to remove a parenthesis after a number in a string:
"dl_CONH_r = a0cons+a2cons*(CONH_r_lag_1)-a3cons*HGDI_r_lag_1)-(1-a3cons)*HNW_r_lag_2)+a4cons*rate_90_r_lag_1))+a5cons*dl_HCOE_r+a6cons*dl_HOY_r_lag_2)+a7cons*dl_HNW_r_lag_1)+a8cons*d_rate_UNE_lag_2)+(1-a5cons-a6cons-a7cons)*(dl_TREND_PROD+dl_TREND_AVEH+dl_TREND_WAP)"
The resulting string should look like this:
"dl_CONH_r = a0cons+a2cons*(CONH_r_lag_1-a3cons*HGDI_r_lag_1-(1-a3cons)*HNW_r_lag_2+a4cons*rate_90_r_lag_1)+a5cons*dl_HCOE_r+a6cons*dl_HOY_r_lag_2+a7cons*dl_HNW_r_lag_1+a8cons*d_rate_UNE_lag_2+(1-a5cons-a6cons-a7cons)*(dl_TREND_PROD+dl_TREND_AVEH+dl_TREND_WAP)"
The regular expression I am trying to capture here is the first parenthesis after the string "lag_" followed by some number. Note, that in places there are two parenthesis:
rate_90_r_lag_1))
And I only want to remove the first one.
I've tried a simple regex in gsub
a <- "dl_CONH_r = a0cons+a2cons*(CONH_r_lag_1)-a3cons*HGDI_r_lag_1)-(1-a3cons)*HNW_r_lag_2)+a4cons*rate_90_r_lag_1))+a5cons*dl_HCOE_r+a6cons*dl_HOY_r_lag_2)+a7cons*dl_HNW_r_lag_1)+a8cons*d_rate_UNE_lag_2)+(1-a5cons-a6cons-a7cons)*(dl_TREND_PROD+dl_TREND_AVEH+dl_TREND_WAP)"
gsub("[0-9]\\)","[0-9]",a)
But I the resulting string removes the number and replaces it with [0-9]:
"dl_CONH_r = a0cons+a2cons*(CONH_r_lag_[0-9]-a3cons*HGDI_r_lag_[0-9]-(1-a3cons)*HNW_r_lag_[0-9]+a4cons*rate_90_r_lag_[0-9])+a5cons*dl_HCOE_r+a6cons*dl_HOY_r_lag_[0-9]+a7cons*dl_HNW_r_lag_[0-9]+a8cons*d_rate_UNE_lag_[0-9]+(1-a5cons-a6cons-a7cons)*(dl_TREND_PROD+dl_TREND_AVEH+dl_TREND_WAP)"
I understand that the gsub is doing what it is intended to do. What I don't know is how to keep the number before the parenthesis?
You need to use a look around (in this case the preceded by) so that it will match just the parentheses as the matching group instead of the numbers and the parentheses. Then you can just remove the parentheses.
gsub("(?<=[0-9])\\)","", a, perl = TRUE)
You can do this using capture groups:
Lets just try it on the string my_string <- " = a0cons+a2cons*(CONH_r_lag_1)-a3cons*"
reg_expression <- "(.*[0-9])\\)(.*)" #two capture groups, with the parenthesis not in a group
my_sub_string <- sub(reg_expression,"\\1\\2", my_string)
Notice "\\1" reads like \1 to the regex engine, and so is a special character referring to the first capture group. (These can also be named)
Another way of doing this is lookarounds:
There are two basic kinds of lookarounds, a lookahead (?=) and a lookbehind (?<=). Since we want to match a pattern, but not capture, something behind our matched expression we need a lookbehind.
reg_expression <- "(?<=[0-9])\\)" #lookbehind
my_sub_string <- sub(reg_expression,"", my_string)
Which will match the pattern, but only replace the parenthesis.
I would like to convert this:
AIR-GEN-SUM-UD-ELA-NH-COMBINED-3-SEG1
to this:
ELA-3
I tried this function:
str_extract(.,pattern = ":?(ELA).*(\\d\\-)"))
it printed this:
"ELA-NH-COMBINED-3-"
I need to get rid of the text or anything between the two extracts. The number will be a number between 3 and 9. How should I modify my expression in pattern =?
Thanks!
1) Match everything up to -ELA followed by anything (.*) up to - followed by captured digits (\\d+)followed by - followed by anything. Then replace that with ELA- followed by the captured digits. No packages are used.
x <- "AIR-GEN-SUM-UD-ELA-NH-COMBINED-3-SEG1"
sub(".*-ELA.*-(\\d+)-.*", "ELA-\\1", x)
## [1] "ELA-3"
2) Another approach if there is only one numeric field is that we can read in the fields, grep out the numeric one and preface it with ELA- . No packages are used.
s <- scan(text = x, what = "", quiet = TRUE, sep = "-")
paste("ELA", grep("^\\d+$", s, value = TRUE), sep = "-")
## [1] "ELA-3"
TL;DR;
You can't do that with a single call to str_extract because you cannot match discontinuous portions of texts within a single match operation.
Again, it is impossible to match texts that are separated with other text into one group.
Work-arounds/Solutions
There are two solutions:
Capture parts of text you need and then join them (2 operations: match + join)
Capture parts of text you need and then replace with backreferences to the groups needed (1 replace operation)
Capturing groups only keep parts of text you match in separate memory buffers, but you also need a method or function that is capable of accessing these chunks.
Here, in R, str_extract drops them, but str_match keeps them in the result.
s <- "AIR-GEN-SUM-UD-ELA-NH-COMBINED-3-SEG1"
m <- str_match(s, ":?(ELA).*-(\\d+)")
paste0(m[,2], "-", m[,3])
This prints ELA-3. See R demo online.
Another way is to replace while capturing the parts you need to keep and then using backreferences to those parts in the replacement pattern:
x <- "AIR-GEN-SUM-UD-ELA-NH-COMBINED-3-SEG1"
sub("^.*-ELA.*?-([^-]+)-[^-]+$", "ELA-\\1", x)
See this R demo
How can I extract digits from a string that can have a structure of xxxx.x or xxxx.x-x and combine them as a number? e.g.
list <- c("1010.1-1", "1010.2-1", "1010.3-1", "1030-1", "1040-1",
"1060.1-1", "1060.2-1", "1070-1", "1100.1-1", "1100.2-1")
The desired (numeric) output would be:
101011, 101021, 101031...
I tried
regexp <- "([[:digit:]]+)"
solution <- str_extract(list, regexp)
However that only extracts the first set of digits; and using something like
regexp <- "([[:digit:]]+\\.[[:digit:]]+\\-[[:digit:]]+)"
returns the first result (data in its initial form) if matched otherwise NA for shorter strings. Thoughts?
Remove all non-digit symbols:
list <- c("1010.1-1", "1010.2-1", "1010.3-1", "1030-1", "1040-1", "1060.1-1", "1060.2-1", "1070-1", "1100.1-1", "1100.2-1")
as.numeric(gsub("\\D+", "", list))
## => [1] 101011 101021 101031 10301 10401 106011 106021 10701 110011 110021
See the R demo online
I have no experience with R but I do know regular expressions. When I look at the pattern you're specifying "([[:digit:]]+)". I assume [[:digit:]] stands for [0-9], so you're capturing one group of digits.
It seems to me you're missing a + to make it capture multiple groups of digits.
I'd think you'd need to use "([[:digit:]]+)+".