Looping grepl() through data.table (R)

Question

I have a dataset stored as a data.table DT that looks like this:

print(DT)
   category            industry
1: administration      admin
2: nurse         


        

Answer 1

As long as the match is always based on the start of the category string, then this works just fine:

dt[substring(category, 1, nchar(industry)) == industry]
#              category industry
# 1:     administration    admin
# 2:           trucking    truck
# 3:     administration    admin
# 4:           trucking    truck
# 5: nurse practitioner    nurse