Question

I’m trying to do a boxplot of a list of values at ggplot2, but the problem is that it doesn’t know how to deal with lists, what should I try ?

E.g.:

k <- list(c(1,2,3,4,5),c(1,2,3,4),c(1,3,6,8,14),c(1,3,7,8,10,37))
k
[[1]]
[1] 1 2 3 4 5

[[2]]
[1] 1 2 3 4

[[3]]
[1]  1  3  6  8 14

[[4]]
[1]  1  3  7  8 10 37

If I pass k as an argument to boxplot() it will handle it flawlessly and produce a nice (well not so nice… hehehe) boxplot with the range of all the values as the Y-axis and the list index (each element) as the X-axis.

How should I achieve the exact same effect with ggplot2 ? I think that dataframes or matrices are not an option because the vectors are of different length.

Thanks

Answer 1

The answer is that you don’t. ggplot2 is designed to work with data frames, particularly long form data frames. That means you need your data as one tall vector, with a grouping factor:

d <- data.frame(x = unlist(k), 
                grp = rep(letters[1:length(k)],times = sapply(k,length)))
ggplot(d,aes(x = grp, y = x)) + geom_boxplot()

And as pointed out in the comments, melt achieves the same result as this manual reshaping and is much simpler. I guess I like to make things difficult.