Split words in R Dataframe column - regex

Question

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)

Answer 1

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))

Answer 2

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"

Answer 3

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"