Use R and regex to keep only desired comma in address string - r

Question

I would like to split a list of address strings into two columns, splitting between City and State.
For example, say I have two address strings:
addr1 <- "123 ABC street Lot 10, Fairfax, VA 22033"
addr2 <- "123 ABC street Fairfax, VA 22033"
How would I use regex in R to remove the 'unexpected' comma between Lot 10 and Fairfax, so that the only comma remaining in any given address string is the comma separating City and State?
My desired result is a dataframe with the address string split into two columns on the abovementioned comma:

Answer 1

There are two ways to expand on Tim's answer:
Zip+4 zip codes (US only?); and
"state" of not-2-letters ... really, just looking for the word-boundary instead of hard-coding "2 letters" (not sure if/when this is a factor ... does anybody write a non-2-letter state?)
addresses <- c("123 ABC street Lot 10, Fairfax, VA 22033", "123 ABC street Fairfax, VA 22033")
sub("\\b[[:alpha:]]+\\s+[[:digit:]]{5}(-[[:digit:]]{4})?$", "", addresses)
# [1] "123 ABC street Lot 10, Fairfax, " "123 ABC street Fairfax, "
sub(".*(\\b[[:alpha:]]+\\s+[[:digit:]]{5}(-[[:digit:]]{4})?$)", "\\1", addresses)
# [1] "VA 22033" "VA 22033"
We can remove commas (gsub(",","",...)) and trim whitespace (trimws(...)) separately.
out <- data.frame(
X1 = sub("\\b[[:alpha:]]+\\s+[[:digit:]]{5}(-[[:digit:]]{4})?$", "", addresses),
X2 = sub(".*(\\b[[:alpha:]]+\\s+[[:digit:]]{5}(-[[:digit:]]{4})?$)", "\\1", addresses)
)
out[] <- lapply(out, function(x) trimws(gsub(",", "", x)))
out
# X1 X2
# 1 123 ABC street Lot 10 Fairfax VA 22033
# 2 123 ABC street Fairfax VA 22033
(Though one may argue for a more-careful removal of commas. shrug)

Answer 2

Assuming you just want to split the address before the final state and zip code, you may use sub as follows:
df$X1 <- sub(", [A-Z]{2} \\d{5}$", "", df$address)
df$X2 <- sub("^.*([A-Z]{2} \\d{5})$", "\\1", df$address)
df
X1 X2
1 123 ABC street Lot 10, Fairfax VA 22033
2 123 ABC street Fairfax VA 22033
Data:
df <- data.frame(address=c("123 ABC street Lot 10, Fairfax, VA 22033",
"123 ABC street Fairfax, VA 22033"), stringsAsFactors=FALSE)