Why do'nt you try the dcast function, in the reshape2 package.
d <- read.delim(
col.names = c("user", "film", "rating", "timestamp")
d <- dcast( d, user ~ film, value.var = "rating" )
Just in case your fields are separated by double colons, you cannot use the sep argument of read.delim
So, you just have to read the file as a single column, split the strings, and concatenate the result.
d <- read.delim("a")
d <- as.character( d[,1] ) # vector of strings
d <- strsplit( d, "::" ) # List of vectors of strings of characters
d <- lapply( d, as.numeric ) # List of vectors of numbers
d <- do.call( rbind, d ) # Matrix
d <- as.data.frame( d )
colnames( d ) <- c( "user", "movie", "rating", "timestamp" )