To understand value labels in R, you need to understand the data structure factor.
You can use the factor function to create your own value lables.
# variable v1 is coded 1, 2 or 3
# we want to attach value labels 1=red, 2=blue, 3=green
mydata$v1 <- factor(mydata$v1,
levels = c(1,2,3),
labels = c("red", "blue", "green"))
# variable y is coded 1, 3 or 5
# we want to attach value labels 1=Low, 3=Medium, 5=High
mydata$v1 <- ordered(mydata$y,
levels = c(1,3, 5),
labels = c("Low", "Medium", "High"))
Use the factor() function for nominal data and the ordered() function for ordinal data. R statistical and graphic functions will then treat the data appriopriately.
Note: factor and ordered are used the same way, with the same arguments. The former creates factors and the later creates ordered factors.