# Convert factors to numbers

November 29, 2007
By

(This article was first published on Quantitative Ecology, and kindly contributed to R-bloggers)

If you have a vector of factors it is easy to get the factor level; however, I always forget how to extract the factor value. I ran into the answer here.
> x<-factor(c(round(rnorm(10),2),"A","B",NA))> x [1] 1.61  1.12  1.26  0.09  -0.13 0.16  -0.03 -0.1  0.09  -0.47  [11] A     B    Levels: -0.03 0.09 -0.1 -0.13 0.16 -0.47 1.12 1.26 1.61 A B> as.numeric(x) [1]  9  7  8  2  4  5  1  3  2  6 10 11 NA> as.numeric(levels(x)[x]) [1]  1.61  1.12  1.26  0.09 -0.13  0.16 -0.03 -0.10  0.09 -0.47     [11]   NA    NA   NAWarning message:NAs introduced by coercion

**UPDATE**
And another method mentioned in the comments (that I like better):

> as.numeric(as.character(x))