mapply recycling arguments

Question

I have written a function that will transform a number in base 10 to another base (I'm only interested in base 2 - 9). My current functions to convert base 10 to base 2 looks like:

cb2 <- function(num){
    td<-{}
    a <- {}
    while (num 2 > 0 ){
        a <- num %% 2
        td <- paste(td,a, sep="")
        num <- as.integer(num / 2)              
    }   
    return(td)  
} 

And the usage would be:

sapply(1:10, cb2)

I realize these numbers are in reverse order, but I will handle reversing the new numbers in a separate function.

I would like to generalize this function and include the preferred base(s) as arguments to the function, ala...

convertbase <- function(num, base){
    td<-{}
    a <- {}
    while (num / base > 0 ){
        a <- num %% base
        td <- paste(td,a, sep="")
        num <- as.integer(num / base)               
    }   
    return(td)  
}

If I'm only interested in a single number converted into base 2-10, all is well:

mapply(convertbase, 10, 2:10)

However, if I want numbers 1:10 for base 2:10, I run into problems:

mapply(convertbase, 1:10, 2:10)
Warning message:
In mapply(convertbase, 1:10, 2:10) :
  longer argument not a multiple of length of shorter

Ideally, this function or set of functions would return a dataframe with separate columns for base 2-10, but I realize there's something missing between the code I have and the goal. Any help would be appreciated.

Answer 1

mapply applies the function to each row, whereas it seems to me that you want to apply the function to all combinations of number and base. This does the trick:

outer(1:10,2:9,Vectorize(convertbase))