I have list of US presidents with speeches about various topics (although some don't have labels) and in the column filename I have something in the format like
1981_Reagan, 1982_economy_Reagan... 1994_Clinton, 1994_criminal_justice_Clinton
(each in a separate row) and I'd like to extract which president spoke. I was going to use a function like sub_str but not sure how to go about extracting the just the name - obviously the different lengths of names are a consideration, but also not wanting to extract unwanted information such as the year or other words.
here is a simple way using strsplit, assuming the president name is always at the end of the string separated from everything by "_":
vec <- c("1981_Reagan",
"1982_economy_Reagan",
"1994_Clinton",
"1994_criminal_justice_Clinton")
sapply(strsplit(vec, "_"), function(x) x[length(x)])
#output
"Reagan" "Reagan" "Clinton" "Clinton"
basically split the strings by "_" and extract the last element from each resulting vector
Another way using regex:
sub(".+_", "", vec)
replace any characters up to _ with nothing. This is greedy so it will replace until the last _.
You can also:
vec <- c("1981_Reagan",
"1982_economy_Reagan",
"1994_Clinton",
"1994_criminal_justice_Clinton")
sub(".*_(\\w+)","\\1",vec,perl=T)
#[1] "Reagan" "Reagan" "Clinton" "Clinton"
My solution seems to be the fastest by using Perl.
vec <- c("1981_Reagan",
"1982_economy_Reagan",
"1994_Clinton",
"1994_criminal_justice_Clinton")
vec <- rep(vec,99999)
f1 <- function(vec) {sub(".*_", "", vec)}
f2 <- function(vec) {sub(".*_(\\w+)","\\1",vec,perl=T)}
f3 <- function(vec) {gsub(".+_", "", vec)}
microbenchmark::microbenchmark( f1(vec), f2(vec), f3(vec),times=100)
#Unit: milliseconds
# expr min lq mean median uq max neval cld
# f1(vec) 212.8052 213.9725 215.5334 215.1973 216.5564 222.4681 100 b
# f2(vec) 133.7839 134.6375 136.0296 135.0752 136.3612 142.8160 100 a
# f3(vec) 290.8456 293.4051 295.5549 294.5525 295.5341 338.8277 100 c
One regularity, at least, in the example input is that the presidents' names (and only their names) are capitalised.
You can capitalise on that...
library(stringr)
str_extract(original_string, "(?<=_)[A-Z][^_]+")
[1] "Reagan" "Reagan" "Clinton" "Clinton"
Where
original_string <- c(
"1981_Reagan",
"1982_economy_Reagan",
"1994_Clinton",
"1994_criminal_justice_Clinton"
)
Related
I have a data frame with words in a column separated by single space. I want to split it into three types as below. Data frame looks as below.
Text
one of the
i want to
I want to split it into as below.
Text split1 split2 split3
one of the one one of of the
I am able to achieve 1st. Not able to figure out the other two.
my code to get split1:
new_data$split1<-sub(" .*","",new_data$Text)
Figured out the split2:
df$split2 <- gsub(" [^ ]*$", "", df$Text)
We can try with gsub. Capture one or more non-white space (\\S+) as a group (in this case there are 3 words), then in the replacement, we rearrange the backreference and insert a delimiter (,) which we use for converting to different columns with read.table.
df1[paste0("split", 1:3)] <- read.table(text=gsub("(\\S+)\\s+(\\S+)\\s+(\\S+)",
"\\1,\\1 \\2,\\2 \\3", df1$Text), sep=",")
df1
# Text split1 split2 split3
#1 one of the one one of of the
#2 i want to i i want want to
data
df1 <- structure(list(Text = c("one of the", "i want to")),
.Names = "Text", class = "data.frame", row.names = c(NA, -2L))
There might be more elegant solutions. Here are two options:
Using ngrams:
library(dplyr); library(tm)
df %>% mutate(splits = strsplit(Text, "\\s+")) %>%
mutate(split1 = lapply(splits, `[`, 1)) %>%
mutate(split2 = lapply(splits, function(words) ngrams(words, 2)[[1]]),
split3 = lapply(splits, function(words) ngrams(words, 2)[[2]])) %>%
select(-splits)
Text split1 split2 split3
1 one of the one one, of of, the
2 i want to i i, want want, to
Extract the two grams manually:
df %>% mutate(splits = strsplit(Text, "\\s+")) %>%
mutate(split1 = lapply(splits, `[`, 1)) %>%
mutate(split2 = lapply(splits, `[`, 1:2),
split3 = lapply(splits, `[`, 2:3)) %>%
select(-splits)
Text split1 split2 split3
1 one of the one one, of of, the
2 i want to i i, want want, to
Update:
With regular expression, we can use back reference of gsub.
Split2:
gsub("((.*)\\s+(.*))\\s+(.*)", "\\1", df$Text)
[1] "one of" "i want"
Split3:
gsub("(.*)\\s+((.*)\\s+(.*))", "\\2", df$Text)
[1] "of the" "want to"
This is a bit of hackish solution.
Assumption :- you are not concerned about number of spaces between two words.
> library(stringr)
> x<-c('one of the','i want to')
> strsplit(gsub('(\\S+)\\s+(\\S+)\\s+(.*)', '\\1 \\1 \\2 \\2 \\3', x), '\\s\\s+')
#[[1]]
#[1] "one" "one of" "of the"
#[[2]]
#[1] "i" "i want" "want to"
I wish to replace all 2's in a string after the first occurrence of a 2, ideally using regex in base R. This seems like it must be a duplicate, but I cannot locate the answer.
Here is an example:
my.data <- read.table(text='
my.string
.1.222.2.2
..1..1..2.
1.1.2.2...
.222.232..
..1..1....
', header=TRUE, stringsAsFactors = FALSE)
my.data
desired.result <- read.table(text='
my.string
.1.2......
..1..1..2.
1.1.2.....
.2....3...
..1..1....
', header=TRUE, stringsAsFactors = FALSE)
desired.result
my.last.2 <- c(4, 9, 5, 2, NA)
my.last.2
Thank you for any assistance.
This appears to match your desired output:
> gsub(pattern = "(?<=2)(.*?)2",
replacement = "\\1\\.",
x = my.data$my.string,
perl = TRUE)
[1] ".1.2......" "..1..1..2." "1.1.2....." ".2....3..." "..1..1...."
This is literally a directly modification from this answer to a very similar question to make it R specific. I'll be honest, I don't quite understand this regex, so use (and up-vote) with caution.
This works, but is probably inefficient:
with(my.data, gsub("#", "2", gsub("2", ".", sub("2", "#", my.string))))
# [1] ".1.2......" "..1..1..2." "1.1.2....." ".2....3..." "..1..1...."
Approach: Use sub to only match the first occurrence and change it to # (or some other placeholder character which doesn't show up elsewhere in my.string, then use gsub to replace all remaining 2s, then gsub # back into 2.
I have some string
string <- "abbccc"
I want to replace the chains of the same letter to just one letter and number of occurance of this letter. So I want to have something like this:
"ab2c3"
I use stringi package to do this, but it doesn't work exactly like I want. Let's say I already have vector with parts for replacement:
vector <- c("b2", "c3")
stri_replace_all_regex(string, "([a-z])\\1{1,8}", vector)
The output:
[1] "ab2b2" "ac3c3"
The output I want: [1] "ab2c3"
I also tried this way
stri_replace_all_regex(string, "([a-z])\\1{1,8}", vector, vectorize_all=FALSE)
but i get error
Error in stri_replace_all_regex(string, "([a-z])\\1{1,8}", vector, vectorize_all = FALSE) :
vector length not consistent with other arguments
Not regex but astrsplit and rle with some paste magic:
string <- c("abbccc", "bbaccc", "uffff", "aaabccccddd")
sapply(lapply(strsplit(string, ""), rle), function(x) {
paste(x[[2]], ifelse(x[[1]] == 1, "", x[[1]]), sep="", collapse="")
})
## [1] "ab2c3" "b2ac3" "uf4" "a3bc4d3"
Not a stringi solution and not a regex either, but you can do it by splitting the string and using rle:
string <- "abbccc"
res<-paste(collapse="",do.call(paste0,rle(strsplit(string,"",fixed=TRUE)[[1]])[2:1]))
gsub("1","",res)
#[1] "ab2c3"
This keeps everything before a period:
gsub("\\..*","", data$column )
how to keep everything after the period?
To remove all the characters before a period in a string(including period).
gsub("^.*\\.","", data$column )
Example:
> data <- 'foobar.barfoo'
> gsub("^.*\\.","", data)
[1] "barfoo"
To remove all the characters before the first period(including period).
> data <- 'foo.bar.barfoo'
> gsub("^.*?\\.","", data)
[1] "bar.barfoo"
You could use stringi with lookbehind regex
library(stringi)
stri_extract_first_regex(data1, "(?<=\\.).*")
#[1] "bar.barfoo"
stri_extract_first_regex(data, "(?<=\\.).*")
#[1] "barfoo"
If the string doesn't have ., this retuns NA (it is not clear about how to deal with this in the question)
stri_extract_first_regex(data2, "(?<=\\.).*")
#[1] NA
###data
data <- 'foobar.barfoo'
data1 <- 'foo.bar.barfoo'
data2 <- "foobar"
If you don't want to think about the regex for this the qdap package has the char2end function that grabs from a particular character until the end of the string.
data <- c("foo.bar", "foo.bar.barfoo")
library(qdap)
char2end(data, ".")
## [1] "bar" "bar.barfoo"
use this :
gsub(".*\\.","", data$column )
this will keep everything after period
require(stringr)
I run a course on Data Analysis and the students came up with this solution :
get_after_period <- function(my_vector) {
# Return a string vector without the characters
# before a period (excluding the period)
# my_vector, a string vector
str_sub(my_vector, str_locate(my_vector, "\\.")[,1]+1)
}
Now, just call the function :
my_vector <- c('foobar.barfoo', 'amazing.point')
get_after_period(my_vector)
[1] "barfoo" "point"
I have some data frame, df with a column with dates that are in the following format:
pv$day
01/01/13 00:00:00
03/01/13 00:02:03
04/03/13 00:10:15
....
I would like to eliminate the timestamp, just leaving the date (e.g. 01/01/13 for the first row). I have tried both using sapply() to apply the strsplit() function, and tried to filter the content using a regex, but don't seem to have quite gotten it right in either case. This:
sapply(pv$day, function(x) strsplit(toString(x), ' '))
gives me the column with the correct split, but indexing with either [1] or [[1]] does not return the first element of the split.
What is the best way to go about this?
You can use sub:
vec <- c("01/01/13 00:00:00", "03/01/13 00:02:03", "04/03/13 00:10:15")
sub(" .+", "", vec)
# [1] "01/01/13" "03/01/13" "04/03/13"
A simple, flexible solution is to use strptime and strftime. Here is an example that uses your dates from the example above:
# Your dates
t <- c("01/01/13 00:00:00","03/01/13 00:02:03", "04/03/13 00:10:15")
# Convert character strings to dates
z <- strptime(t, "%d/%m/%y %H:%M:%OS")
# Convert dates to string, omitting the time
z.date <- strftime(z,"%d/%m/%y")
# Print the first date
z.date[1]
Here's a nice way to use sapply, it uses strsplit to split at the space
> d <- c("01/01/13 00:00:00", "03/01/13 00:02:03", "04/03/13 00:10:15")
> sapply(strsplit(d, " "), `[`, 1)
# [1] "01/01/13" "03/01/13" "04/03/13"
And also, you could use stringr::word if you just want a character vector.
> library(stringr)
> word(d)
# [1] "01/01/13" "03/01/13" "04/03/13"
Here is an approach using a look around assertion:
vec <- c("01/01/13 00:00:00", "03/01/13 00:02:03", "04/03/13 00:10:15")
gsub(pattern = "(?=00).*$", replacement = "", vec, perl = TRUE)
[1] "01/01/13 " "03/01/13 " "04/03/13 "
The pattern looks for anything at the end of a string that begins with double 00, and removes it.