How to insert a character every n characters from end of string
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I would like to insert a colon every five characters starting from the end of the string, preferably using regex and gsub in R.
text <- "My Very Enthusiastic Mother Just Served Us Noodles!"
I have been able to insert a colon every five characters from beginning of the text using:
gsub('(.{5})', "\1:", text, perl = T)
I have written an inelegant function for achieving this as follows:
library(dplyr)
str_reverse<-function(x){
strsplit(x,split='')[[1]] %>% rev() %>% paste(collapse = "")
}
text2<-str_reverse(text)
text3<-gsub('(.{5})', "\1:", text2, perl = T)
str_reverse(text3)
to get the desired result
[1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
Is there a way this can be achieved directly using regular expressions?
r regex
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
add a comment |
I would like to insert a colon every five characters starting from the end of the string, preferably using regex and gsub in R.
text <- "My Very Enthusiastic Mother Just Served Us Noodles!"
I have been able to insert a colon every five characters from beginning of the text using:
gsub('(.{5})', "\1:", text, perl = T)
I have written an inelegant function for achieving this as follows:
library(dplyr)
str_reverse<-function(x){
strsplit(x,split='')[[1]] %>% rev() %>% paste(collapse = "")
}
text2<-str_reverse(text)
text3<-gsub('(.{5})', "\1:", text2, perl = T)
str_reverse(text3)
to get the desired result
[1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
Is there a way this can be achieved directly using regular expressions?
r regex
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
Consider that thestringipackage has thestri_reversefunction already available and super efficient.
– nicola
Nov 16 '18 at 12:45
add a comment |
I would like to insert a colon every five characters starting from the end of the string, preferably using regex and gsub in R.
text <- "My Very Enthusiastic Mother Just Served Us Noodles!"
I have been able to insert a colon every five characters from beginning of the text using:
gsub('(.{5})', "\1:", text, perl = T)
I have written an inelegant function for achieving this as follows:
library(dplyr)
str_reverse<-function(x){
strsplit(x,split='')[[1]] %>% rev() %>% paste(collapse = "")
}
text2<-str_reverse(text)
text3<-gsub('(.{5})', "\1:", text2, perl = T)
str_reverse(text3)
to get the desired result
[1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
Is there a way this can be achieved directly using regular expressions?
r regex
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
I would like to insert a colon every five characters starting from the end of the string, preferably using regex and gsub in R.
text <- "My Very Enthusiastic Mother Just Served Us Noodles!"
I have been able to insert a colon every five characters from beginning of the text using:
gsub('(.{5})', "\1:", text, perl = T)
I have written an inelegant function for achieving this as follows:
library(dplyr)
str_reverse<-function(x){
strsplit(x,split='')[[1]] %>% rev() %>% paste(collapse = "")
}
text2<-str_reverse(text)
text3<-gsub('(.{5})', "\1:", text2, perl = T)
str_reverse(text3)
to get the desired result
[1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
Is there a way this can be achieved directly using regular expressions?
r regex
r regex
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
edited Nov 16 '18 at 12:29
Sotos
31.2k51741
31.2k51741
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
asked Nov 16 '18 at 12:14
Joseph KigothoJoseph Kigotho
226
226
Consider that thestringipackage has thestri_reversefunction already available and super efficient.
– nicola
Nov 16 '18 at 12:45
add a comment |
Consider that thestringipackage has thestri_reversefunction already available and super efficient.
– nicola
Nov 16 '18 at 12:45
Consider that the
stringi package has the stri_reverse function already available and super efficient.– nicola
Nov 16 '18 at 12:45
Consider that the
stringi package has the stri_reverse function already available and super efficient.– nicola
Nov 16 '18 at 12:45
add a comment |
1 Answer
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You may use
gsub('(?=(?:.{5})+$)', ":", text, perl = TRUE)
## => [1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
See the regex demo
The (?=(?:.{5})+$) pattern matches any location inside the string that is followed with any 5 chars (other than line break chars) 1 or more times up to the end of the string.
If the input string can contain line breaks you need to add (?s) at the start of the pattern (since . in PCRE regex does not match line breaks by default):
'(?s)(?=(?:.{5})+$)'
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,(?=(?:.{5})+?$)=(?=(?:.{5})+$)because the next pattern is$, end of string and.{5}goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.
– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
add a comment |
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You may use
gsub('(?=(?:.{5})+$)', ":", text, perl = TRUE)
## => [1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
See the regex demo
The (?=(?:.{5})+$) pattern matches any location inside the string that is followed with any 5 chars (other than line break chars) 1 or more times up to the end of the string.
If the input string can contain line breaks you need to add (?s) at the start of the pattern (since . in PCRE regex does not match line breaks by default):
'(?s)(?=(?:.{5})+$)'
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,(?=(?:.{5})+?$)=(?=(?:.{5})+$)because the next pattern is$, end of string and.{5}goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.
– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
add a comment |
You may use
gsub('(?=(?:.{5})+$)', ":", text, perl = TRUE)
## => [1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
See the regex demo
The (?=(?:.{5})+$) pattern matches any location inside the string that is followed with any 5 chars (other than line break chars) 1 or more times up to the end of the string.
If the input string can contain line breaks you need to add (?s) at the start of the pattern (since . in PCRE regex does not match line breaks by default):
'(?s)(?=(?:.{5})+$)'
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,(?=(?:.{5})+?$)=(?=(?:.{5})+$)because the next pattern is$, end of string and.{5}goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.
– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
add a comment |
You may use
gsub('(?=(?:.{5})+$)', ":", text, perl = TRUE)
## => [1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
See the regex demo
The (?=(?:.{5})+$) pattern matches any location inside the string that is followed with any 5 chars (other than line break chars) 1 or more times up to the end of the string.
If the input string can contain line breaks you need to add (?s) at the start of the pattern (since . in PCRE regex does not match line breaks by default):
'(?s)(?=(?:.{5})+$)'
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
You may use
gsub('(?=(?:.{5})+$)', ":", text, perl = TRUE)
## => [1] "M:y Ver:y Ent:husia:stic :Mothe:r Jus:t Ser:ved U:s Noo:dles!"
See the regex demo
The (?=(?:.{5})+$) pattern matches any location inside the string that is followed with any 5 chars (other than line break chars) 1 or more times up to the end of the string.
If the input string can contain line breaks you need to add (?s) at the start of the pattern (since . in PCRE regex does not match line breaks by default):
'(?s)(?=(?:.{5})+$)'
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
answered Nov 16 '18 at 12:17
Wiktor StribiżewWiktor Stribiżew
329k16149228
329k16149228
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,(?=(?:.{5})+?$)=(?=(?:.{5})+$)because the next pattern is$, end of string and.{5}goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.
– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
add a comment |
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,(?=(?:.{5})+?$)=(?=(?:.{5})+$)because the next pattern is$, end of string and.{5}goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.
– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
1
1
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,
(?=(?:.{5})+?$) = (?=(?:.{5})+$) because the next pattern is $, end of string and .{5} goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.– Wiktor Stribiżew
Nov 16 '18 at 12:46
@AndreElrico 1) It does not matter if you use lazy or greedy quantifiers here,
(?=(?:.{5})+?$) = (?=(?:.{5})+$) because the next pattern is $, end of string and .{5} goes matching up to the end of the string anyway, 2) since the regex searches for matches from left to right, the 2nd position is matched, not the 5 from the end. PCRE regex cannot be set to search from the end.– Wiktor Stribiżew
Nov 16 '18 at 12:46
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
thanks you also found this here rexegg.com/regex-quantifiers.html#longest_shortest . this was a missing piece in my brain
– Andre Elrico
Nov 16 '18 at 12:49
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
@AndreElrico You may want to read my quantfier explanations, too.
– Wiktor Stribiżew
Nov 16 '18 at 12:53
add a comment |
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Consider that the
stringipackage has thestri_reversefunction already available and super efficient.– nicola
Nov 16 '18 at 12:45