Keep only the first letter of each word after a comma - r

Question

I have strings like Sacher, Franz Xaver or Nishikawa, Kiyoko.
Using R, I want to change them to Sacher, F. X. or Nishikawa, K..
In other words, the first letter of each word after the comma should be retained with a dot (and a whitespace if another word follows).
Here is a related response, but it cannot be applied to my case 1:1 as it does not have a comma in its strings; it seems that the simple addition of (<?=, ) does not work.
E.g. in the following attempts, gsub() replaces everything, while my str_replace_all()-attempt leads to an error:
TEST <- c("Sacher, Franz Xaver", "Nishikawa, Kiyoko", "Al-Assam, Muhammad")
# first attempt
# (resembles the response from the other thread)
gsub('\\b(\\pL)\\pL{2,}|.','\\U\\1', TEST, perl = TRUE)
# second attempt
# error: "Incorrect unicode property"
stringr::str_replace_all(TEST, '(?<=, )\\b(\\pL)\\pL{2,}|.','\\U\\1')
I would be grateful for your help!

Answer 1

You can use
gsub("(*UCP)^[^,]+(*SKIP)(*F)|\\b(\\p{L})\\p{L}*", "\\U\\1.", TEST, perl=TRUE)
See the regex demo. Details:
(*UCP) - the PCRE verb that will make \b Unicode aware
^[^,]+(*SKIP)(*F) - start of string and then any zero or more chars other than a comma, and then the match is failed and skipped, the next match starts at the location where the failure occurred
| - or
\b - word boundary
(\p{L}) - Group 1: any Unicode letter
\p{L}* - zero or more Unicode letters
See the R demo:
TEST <- c("Sacher, Franz Xaver", "Nishikawa, Kiyoko", "Al-Assam, Muhammad")
gsub("(*UCP)^[^,]+(*SKIP)(*F)|\\b(\\p{L})\\p{L}*", "\\U\\1.", TEST, perl=TRUE)
## => [1] "Sacher, F. X." "Nishikawa, K." "Al-Assam, M."

Answer 2

A crude approach splitting the string :
TEST <- c("Sacher, Franz Xaver", "Nishikawa, Kiyoko", "Al-Assam, Muhammad")
sapply(strsplit(TEST, '\\s+'), function(x)
paste0(x[1], paste0(substr(x[-1], 1, 1), collapse = '.'), '.'))
#[1] "Sacher,F.X." "Nishikawa,K." "Al-Assam,M."

Answer 3

An approach using multiple backreference:
gsub("(\\b\\w+,\\s)(\\b\\w).*(\\b\\w)*", "\\1\\2.\\3", TEST)
[1] "Sacher, F." "Nishikawa, K." "Al-Assam, M."
Here, we use three capturing groups to refer back to in gsub's replacment argument via backreference:
(\\b\\w+,\\s): this, first, group captures the last name plus the comma followed by whitespace
(\\b\\w): this, second, group captures the initial of the first name
(\\b\\w): this, third, group captures the initial of the middle name