Extracting Words of specific length in R using regular expressions

Question

I have a code like (I got it here):

m<- c("Hello! #London is gr8. I really likewhatishappening here! The alcomb of Mount Everest is excellent! the aforementioned place is amazing! #Wow")

x<- gsub("\\<[a-z]\\{4,10\\}\\>","",m)
x

I tried other ways of doing it, like

m<- c("Hello! #London is gr8. I really likewhatishappening here! The alcomb of Mount Everest is excellent! the aforementioned place is amazing! #Wow")

x<- gsub("[^(\\b.{4,10}\\b)]","",m)
x

I need to remove words which are lesser than 4 or greater than 10 in length. Where am I going wrong?

Answer 1

  gsub("\\b[a-zA-Z0-9]{4,10}\\b", "", m) 
 "! # is gr8. I  likewhatishappening ! The  of   is ! the aforementioned  is ! #Wow"

Let's explain the regular expression terms :

1. \b matches at a position that is called a "word boundary". This match is zero-length.
2. [a-zA-Z0-9] :alphanumeric
3. {4,10} :{min,max}

if you want to get the negation of this so , you put it between() and you take //1

gsub("([\\b[a-zA-Z0-9]{4,10}\\b])", "//1", m) 

"Hello! #London is gr8. I really likewhatishappening here! The alcomb of Mount Everest is excellent! the aforementioned place is amazing! #Wow"

It is funny to see that words with 4 letters exist in the 2 regexpr.

Answer 2

# starting string
m <- c("Hello! #London is gr8. I really likewhatishappening here! The alcomb of Mount Everest is excellent! the aforementioned place is amazing! #Wow")

# remove punctuation (optional)
v <- gsub("[[:punct:]]", " ", m)

# split into distinct words
w <- strsplit( v , " " )

# calculate the length of each word
x <- nchar( w[[1]] )

# keep only words with length 4, 5, 6, 7, 8, 9, or 10
y <- w[[1]][ x %in% 4:10 ]

# string 'em back together
z <- paste( unlist( y ), collapse = " " )

# voila
z