Iterate a characters or numbers in a loop in R

Question

Quite new to R so this may be an easy answer. I have a list of characters. I want to remove the last letter and iterate it by one so A becomes B, 1 becomes 2 etc.

waferlist<-c('L2MLQ','L2MIW','L2MK0','L2ML6','L2MO2','L2MHE','L2MK4','L2MN6','L2MLM')

for (i in waferlist)
{

lastchar<-substr(i,5,6)           #Get last character

k<-lastchar==LETTERS             #Is it a Letter

pos<-min(which(k==TRUE))        #Find letter position and itterate
pos<-pos+1
pos<-LETTERS[pos]

The problem I'm having is if the last character is a number, it returns it as an Inf or NA_character_ as its not in LETTERS.

I've tried to find a way to select these non results below but it doesn't see it as a TRUE/FALSE statement so it doesn't work. Is there another way to do this?

     if(pos==Inf | pos==NA_character_)
    {
       lastchar<-as.numeric(lastchar)
       pos<-lastchar+1
    }

Answer 1

For an efficient solution (assuming you are using capitals),

res <- sapply(waferlist, function(i) {
    out <- utf8ToInt(i)
    out[[nchar(i)]] <- out[[nchar(i)]] + 1
    if (out[[nchar(i)]] == 91) out[[nchar(i)]] <- 65
    ## For 9 cycling back to 0?
    else if (out[[nchar(i)]] == 58) out[[nchar(i)]] <- 48
    intToUtf8(out)
})