Get the strings before the comma with R

Just for fun, you can use strsplit

> x <- c("London, UK", "Paris, France", "New York, USA")
> sapply(strsplit(x, ","), "[", 1)
[1] "London"   "Paris"    "New York"

You can use gsub with a bit of regexp :

cities <- gsub("^(.*?),.*", "\\1", df$city)

This one works, too :

cities <- gsub(",.*$", "", df$city)