Problem #8 on the Project Euler problem list requires finding the greatest product of five consecutive digits in a large string of integers.
For this problem, I copied and pasted the large number into a file, and read it in using scan(). As there were line breaks in the copied and pasted numbers, I used paste() with the collapse argument to restore it to a single line. From there, it was a matter of taking 5-character substrings, converting them to numbers, and using prod() to calculate the product of each group of 5 numbers.
gprod <- function() { # Read number as string snum <- scan(file="number.dat", what=character(0), strip.white=TRUE, quiet=TRUE) # Concatenate lines into a single line snum <- paste(snum, collapse="", sep="") mp <- 0 for (i in 1:(nchar(snum)-4)) { s <- substr(snum, i, i+4) m <- prod(as.numeric(strsplit(s,"")[[1]])) if (m > mp) { mp <- m } } mp }