Keep Coding

for the purposes of GLM modeling, I am trying to change the qualitative values for a variable to quantitative "dummy" variables. For this exercise, I am using Plyr, which seems incredibly intuitive over base R.
str(data$Socks)
$ Socks : Factor w/ 4 levels "1+","2+","4+","8+" ..: 1 4 4 1 4 4 1 4 1 1 ...
levels(data$Socks)
[1] "1" "2+" "4+" "8+"
library(dplyr)
select(data, Socks)
2 8+
3 8+
4 1
5 8+
When I try to change the levels, every factor but 1 is changed to an "NA".
data <- data %>% mutate(Socks = factor(Socks, levels = c(1, 2, 4, 8)))
select(data, Socks)
990 1
991 <NA>
992 1
993 <NA>
I would like the values "1","2+","4+","8+" to change to "1", "2", "4", "8".
Any help would be appreciated. Thank you!