plot area truncated when using geom_dotplot - r

Question

consider the following example data:
ex = structure(list(group = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 1L,
2L, 3L, 4L, 6L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 6L, 1L,
2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L, 5L, 1L, 2L, 3L, 4L, 5L, 6L,
1L, 2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L,
5L, 6L, 1L, 2L, 1L, 2L, 3L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 5L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 5L, 1L, 1L, 1L,
4L), .Label = c("A", "B", "C", "D", "E", "F"), class = "factor"),
ID = structure(c(35L, 35L, 35L, 35L, 35L, 35L, 1L, 1L, 1L,
1L, 1L, 6L, 6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 9L, 9L,
9L, 9L, 9L, 9L, 10L, 10L, 10L, 10L, 10L, 11L, 11L, 11L, 11L,
11L, 11L, 12L, 12L, 12L, 12L, 12L, 12L, 13L, 13L, 13L, 13L,
13L, 13L, 14L, 14L, 14L, 14L, 14L, 14L, 21L, 21L, 22L, 22L,
22L, 22L, 2L, 3L, 4L, 5L, 8L, 15L, 16L, 17L, 18L, 19L, 19L,
20L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 30L, 30L, 31L, 32L,
33L, 34L), .Label = c("10", "107", "108", "109", "124", "17",
"18", "187", "19", "21", "24", "26", "27", "28", "335", "336",
"339", "340", "341", "342", "38", "39", "576", "577", "578",
"579", "580", "581", "582", "583", "584", "585", "586", "592",
"6"), class = "factor"), value = c(1L, 7L, 4L, 4L, 3L, 9L,
1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 1L, 5L, 1L, 2L, 1L, 2L, 2L,
2L, 1L, 33L, 27L, 28L, 21L, 28L, 1L, 3L, 1L, 1L, 1L, 1L,
2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 3L, 3L, 2L, 4L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 2L, 1L, 1L, 1L, 1L)), class = "data.frame",
row.names = c(NA, -88L), .Names = c("group", "ID", "value")
)
Note that in group A, value = 1 for every ID. I use ggplot2 to create dot plot based on counts of the value variable using geom_dotplot and faceting by group:
ggplot(ex) + aes(x = value) +
geom_dotplot(binwidth = 1, method = "histodot") +
facet_wrap(~ group)
The dot stack in the first facet is cut off, even when exported using ggsave. Changing the y-axis limits has no effect, but changing the aspect ratio so that H >= W seems to fix the issue (usually by adding way more space to the top than necessary). Is this a bug, or am I specifying my dot plot incorrectly?
EDIT
One workaround is to flip my dotplot and bin by the y variable:
ggplot(ex) + aes(x = group, y = value) +
geom_dotplot(binwidth = 1, method = "histodot",
binaxis = "y", stackdir = "centerwhole") +
facet_wrap(~ group, scales = "free_x")

Answer 1

Two other parameters that can help you are stackratio and dotsize. For example:
ggplot(ex) + aes(x = value) +
geom_dotplot(binwidth = 1, method = "histodot", stackratio = 0.9, dotsize = .75) +
facet_wrap(~ group) +
scale_y_continuous(NULL, breaks = NULL)
You would need to tweak the numbers until you got the layout you wanted.

Answer 2

I found an interesting workaround using geom_bar that achieves the same structure as a dot plot but with rectangles:
ggplot(ex) + aes(x = value, group = ID) +
geom_bar(color = "black", fill = "white", width = 1) +
facet_wrap(~ group)
Although it results in rectangles (rather than dots) and you can't control the stack spacing. The rectangles get resized according to the plot window, which would be equivalent to tweaking the dot size in geom_dotplot. Also, it begs the question "why not just use a regular bar plot?"