How do I manually change the key labels in a legend in ggplot2

Question

I am preparing a plot for publication. I created a stacked box plot to show frequency of patients in each group who were some complicated accumulation of seronegatives versu

Answer 1

I found a hybrid way of doing it. It does relabel the factor but I do not have to do it in the dataframe. Instead I just do it in the ggplot command.

ggplot(data, aes(grp, fill=factor(outcome,labels=c("low","high")))) + 
  geom_bar() +xlab("group") +ylab("number of subjects") +
   labs(fill="Serologic response")

Are there any other ways?