23

I want to add a title to a ggvis plot. I can't find an example anywhere. It's simple to do with other R plots, e.g.

library(ggplot2)
library(ggvis)
x <- 1:10
y <- x^2
df <- data.frame(x, y)

plot(x, y, main = "Plot Title")  # Base R with title
ggplot(df, aes(x, y)) + geom_point() + ggtitle("Plot Title")  # ggplot2 with title
df %>% ggvis(~x, ~y) %>% layer_points()  # ggvis but no title??

Feel like I'm missing something obvious. Any help appreciated.

Anto
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3 Answers3

34

Well, seems like it has not been implemented (or documented?) yet. I'm pretty sure this will be added soon. For now, you can use a dirty hack like so:

df %>% ggvis(~x, ~y) %>% layer_points() %>% 
  add_axis("x", title = "X units") %>%
  add_axis("x", orient = "top", ticks = 0, title = "Plot Title",
           properties = axis_props(
             axis = list(stroke = "white"),
             labels = list(fontSize = 0)))

Furthermore, if you would like to use this hack multiple times, you can create a shorthand for it.

add_title <- function(vis, ..., x_lab = "X units", title = "Plot Title") 
{
  add_axis(vis, "x", title = x_lab) %>% 
    add_axis("x", orient = "top", ticks = 0, title = title,
             properties = axis_props(
               axis = list(stroke = "white"),
               labels = list(fontSize = 0)
             ), ...)
}
df %>% ggvis(~x, ~y) %>% layer_points() %>% add_title() #same as before
df %>% ggvis(~x, ~y) %>% layer_points() %>% add_title(title = "Hello", x_lab = "ton")

Edit:

Now you can set both the main title and the x axis label simultaneously, fixing the overlap mentioned below.

tonytonov
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  • Thanks Tony. Sometimes hacks can be more trouble than they're worth but this is neat! – Anto Jul 31 '14 at 16:27
  • You are welcome! I'll try to remember to update this post as soon as a more elegant native solution appears. – tonytonov Aug 01 '14 at 05:45
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    Unfortunately this hack is incompatible with setting a label on the actual x-axis. The following shows that the x-axis label overlaps the original label "wt" when add_title() is used. Looks like a bug in ggvis. `mtcars %>% ggvis(~wt, ~mpg) %>% layer_points() %>% add_axis("x", title = "long axis label") %>% add_title(title = "Any Title")` – Chris Warth Oct 20 '14 at 20:31
  • @ChrisWarth Try the fix I've proposed, seems to do the job. – tonytonov Oct 23 '14 at 06:32
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    @dsh Despite your suggested edit was rejected by reviewers, it was actually helpful. I updated the answer and made sure it works, though I left out the `type = ` specification since it's redundant (supported by the first example in `?add_axis`). Anyway, just wanted to say thanks for your effort and the meaningful edit explanation. – tonytonov Jan 13 '15 at 09:07
  • @tonytonov Any idea how I can write the title on two separate lines? Especially when I have a very long title. – HNSKD Sep 06 '16 at 02:44
  • Seems like it's [not implemented yet](https://github.com/rstudio/ggvis/issues/359). Workaround: add another axis and set `title_offset`, e.g. to 10. – tonytonov Sep 06 '16 at 08:32
5

Also, to change the font size of the title use this code (adapted from @tonytonov's answer):

add_title <- function(vis, ..., x_lab = "X units", title = "Plot Title") 
{
  add_axis(vis, "x", title = x_lab) %>% 
    add_axis("x", orient = "top", ticks = 0, title = title,
             properties = axis_props(
               axis = list(stroke = "white"),
               title = list(fontSize = 32),
               labels = list(fontSize = 0)
             ), ...)
}
resamsel
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3

I updated @tonytonov's answer to not interfere with the default X axis. It is still implemented as an axis, but implements its own 'title' scale and properly merges user-supplied title properties like fontsize and color with the default properties needed to make the axis invisible. This version hides the axis without presuming a particular background color. Three examples follow the function.

library(ggvis)

# ggvis lacks a plot title function, so add one.
# based on clever hack by tonytonov
# http://stackoverflow.com/a/25030002/1135316
add_title <- function(vis, ..., properties=NULL, title = "Plot Title") 
{
    # recursively merge lists by name
    # http://stackoverflow.com/a/13811666/1135316
    merge.lists <- function(a, b) {
        a.names <- names(a)
        b.names <- names(b)
        m.names <- sort(unique(c(a.names, b.names)))
        sapply(m.names, function(i) {
                   if (is.list(a[[i]]) & is.list(b[[i]])) merge.lists(a[[i]], b[[i]])
                   else if (i %in% b.names) b[[i]]
                   else a[[i]]
               }, simplify = FALSE)
    }

    # default properties make title 'axis' invisible
    default.props <- axis_props(
        ticks = list(strokeWidth=0),
        axis = list(strokeWidth=0),
        labels = list(fontSize = 0),
        grid = list(strokeWidth=0)
        )
    # merge the default properties with user-supplied props.
    axis.props <- do.call(axis_props, merge.lists(default.props, properties))

    # don't step on existing scales.
    vis <- scale_numeric(vis, "title", domain = c(0,1), range = 'width')
    axis <- ggvis:::create_axis('x', 'title', orient = "top",  title = title, properties = axis.props, ...)
    ggvis:::append_ggvis(vis, "axes", axis)
}

# add title with default X axis.
iris %>% 
  ggvis(x = ~Petal.Width) %>% 
  layer_points(y = ~Petal.Length, fill = ~Species) %>%
  add_title(title = "Petal.Width vs. Petal.Length")

# Add title with overridden X axis
iris %>% 
  ggvis(x = ~Petal.Width) %>% 
  layer_points(y = ~Petal.Length, fill = ~Species) %>%
  add_axis("x", title = "X-axis!!!!", title_offset=40,
           properties = axis_props(title=list(fontSize=16),
               labels = list(fontSize = 12))) %>%
  add_title(title = "Petal.Width vs. Petal.Length")

# Change the font size of the title.
iris %>% 
  ggvis(x = ~Petal.Width) %>% 
  layer_points(y = ~Petal.Length, fill = ~Species) %>%
  add_title(title = "Petal.Width vs. Petal.Length",
            properties = axis_props(title=list(fontSize=20)))
Chris Warth
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