[R] Using grep to determine value of last letter...

[Jason Rupert]

I am currently being defeated by grep.  I am attempting to determine the value of the last letter of a character string.  

An example of my data set is shown below.  Regarding the codes, I would like to identify the value of the last character and then take the appropriate action, e.g. 
If the value is L then label UL rating XXX
It the value is F then label UL rating YYY
...

I assume it will be something like the following:
grep("last letter",  HousesWithCodes$Codes) 

Thanks again for any insights. 

BuildYear<-c(1980, 1985, 1975, 1990, 1980)
SqrFootage<-c(1500, 1650, 1500, 2000, 1450)
Exterior<-c("Brick", "Stone", "Siding", "Brick", "Siding")

SubdivisionHouses<-data.frame(BuildYear, SqrFootage, Exterior)

Year<-c(1980, 1985, 1975, 1990, 1977, 1986)
Codes<-c("G2G1L", "G5L1F", "K1Y2G", "G4B1B", "K1N3B", "K3M4X")
BuildingCodes<-data.frame(Year, Codes)

HousesWithCodes<-merge(SubdivisionHouses, BuildingCodes, by.x="BuildYear", by.y="Year")