How to plot frequency of Y N data against age ranges in R

Question

I have a set of data with age ranges (20-29, 30-39, etc.) in one column, and I have people who answered Yes, No, Maybe, Skip. What I need is to plot the frequencies of answers for each age group.

qplot(x=AgeGroup, y=answer, colour = factor(answer), facets = ~ answer,  data = y_n, geom = "line") + guides(colour=FALSE)

This is my code so far, but I think my problem is that my 'y' input is people's answer, rather than the frequency of answers.