regex - extract comma separated strings -

i have data frame below. sample set data uniform looking patterns whole data not uniform:

locationid      address      1073744023  525 east 68th street, new york, ny      10065, usa 1073744022  270 park avenue, new york, ny 10017, usa       1073744025  rockefeller center, 50 rockefeller plaza, new york, ny 10020, usa  1073744024  1251 avenue of americas, new york, ny 10020, usa 1073744021  1301 avenue of americas, new york, ny 10019, usa  1073744026  44 west 45th street, new york, ny 10036, usa 

i need find city , country name address. tried following:

1) strsplit gives me list cannot access last or third last element this.

2) regular expressions finding country easy

str_sub(str_extract(address, "\\d{5},\\s.*"),8,11) 

but city

str_sub(str_extract(address, ",\\s.+,\\s.+\\d{5}"),3,comma_pos) 

i cannot find comma_pos leads me same problem again. believe there more efficient way solve using of above approached.

split data

 ss <- strsplit(data,",")` 

then

n <- sapply(s,len) 

will give number of elements (so can work backward). then

mapply(ss,"[[",n) 

gives last element. or do

sapply(ss,tail,1) 

to last element.

to second-to-last (or more generally) need

sapply(ss,function(x) tail(x,2)[1])