[R] Is it possible to transform a factor to a number like this way?

[Erik Iverson]

song song wrote:
> such a factor as   a=as.factor(c(1.23, 4.56, 7.89))  and I want to get this
> vector: c(1.23, 4.56, 7.89).

You're told how to do this in the help page for ?factor.  See the 
Warning section.