using lapply for nested loops

Question

I have been learning a bit of lapply magic in R, but have not figured out how to replace nested loops -- is this also possible?

Here's my problem, and the nested-loop solution.

monCode <- c('F', 'G', 'H', 'J', 'K', 'M', 'N', 
        'Q', 'U', 'V', 'X', 'Z')
yearRange <- as.character(3:15)
yearRange[as.numeric(yearRange) < 10] <- as.character(paste0("0", yearRange[as.numeric(yearRange) < 10]))

outList <- vector()
for(Yr in yearRange) {
    for (mon in monCode) {
        outList <- c(outList, (paste0("IB", mon, Yr, " Comdty")))
    }
}

How would i do this using nested lapply functions, rather than nested loops?

thanks in advance

Answer 1

No need for nested loops or nested lapply.

Use expand.grid to create all your combinations of monCode and yearRange then do.call(sprintf,...) to concatenate them

f <- expand.grid(monCode,yearRange)
outList <- do.call(sprintf, c(f, fmt = 'IB%s%s comdty'))