Remove legend labels using label = FALSE in guide_legend, or labels = NULL in discrete_scale

Question

As a part of a more complex plot with several legends, one of the legends has only one entry. I want to remove the label from this particular legend and keep only the (edited) title.

df <- data.frame(x = 1, y = 1)

p <- ggplot(df, aes(x = x, y = y, color = factor(x))) + 
       geom_point()
p

Because I do some other manipulations of the legends using guides(foo = guide_legend(override.aes, I was hoping to remove the labels in the same guide_legend call using the label argument.

From ?guide.legend:
"label: [...] If FALSE then the labels are invisible."

Thus, I tried:

p + guides(color = guide_legend(title = "other",
                                label = FALSE))

But this gives an error:

# Error in (function (name)  : grob 'NULL' not found

I then had a look at discrete_scale, which has a labels argument (now with an "s"). From ?discrete_scale:
"labels: NULL for no labels."

Thus, I tried:

p + scale_color_discrete(name = "other",
                         labels = NULL)

...which generates an error:

# Error in data.frame(values = scale_map(scale, breaks), labels = I(scale_labels(scale)),  : 
#                      arguments imply differing number of rows: 1, 0

My current workaround is:

p + scale_color_discrete(name = "other",
                         labels = "")

However, as described above, I would prefer to remove the labels using guide_legend call.

So my main question is:
How can I make label = FALSE in guide_legend work?

If the answer is "it's just doesn't work", how is the "labels: NULL for no labels." supposed to be used in scale_foo_bar?

Answer 1

Both label = FALSE in guide_legend and labels = NULL in discrete_scale are fixed in the development version ggplot2_1.0.1.9002.

# install development version, see https://github.com/hadley/ggplot2/.
# install.packages("devtools")
devtools::install_github("hadley/scales")
devtools::install_github("hadley/ggplot2movies")
devtools::install_github("hadley/ggplot2")

p + guides(color = guide_legend(title = "other", label = FALSE))
# or:
# p + scale_color_discrete(name = "other", labels = NULL)