How to substring every element in vector of strings?

Question

I have the vector:

v <- c("godzilla", "jurassic", "googly")

I want the first 3 letters of every element in this vector. I would like to end up with:

# "god"   "jur"   "goo"

I have already tried using apply , but it didn't work. What should I do?

Answer 1

One option is substring() :

> substring(v, first = 1, last = 3)
[1] "god" "jur" "goo"

or also the R version, substr()

> substr(v, start = 1, stop = 3)
[1] "god" "jur" "goo"

Note the different names for the initial and last character you want.

As both of these functions are vectorised, there is no need for apply() and friends here.

Answer 2

For the fun you can use a regular expression here :

sub('(^.{3}).*','\\1',v)
[1] "god" "jur" "goo"

Which is a another vectorized solution.

Answer 3

@Gavin Simpson's answer is the right way to go, but if you want to use apply() and friends here, you can try the following:

> sapply(strsplit(v, ""), function(x) paste0(x[1:3], collapse=""))
[1] "god" "jur" "goo"

Answer 4

A stringr option is str_sub :

str_sub(v, 1, 3)
#[1] "god" "jur" "goo"

And str_sub_all for multiple substrings in each string:

str_sub_all(v, c(1, 2), c(3, 4))
# [[1]]
# [1] "god" "odz"
# 
# [[2]]
# [1] "jur" "ura"
# 
# [[3]]
# [1] "goo" "oog"