为 ggvis 添加绘图标题

Question

我想为 ggvis 绘图添加标题。我在任何地方都找不到示例。使用其他 R 图很简单，例如

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??

感觉好像我遗漏了一些明显的东西。任何帮助表示赞赏。

Answer 1

嗯，似乎它还没有实施（或记录在案？）。我很确定这将很快添加。现在，您可以像这样使用肮脏的 hack：

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)))

此外，如果您想多次使用此 hack，您可以为其创建一个简写。

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")

编辑：

现在您可以同时设置主标题和 x 轴标签，修复下面提到的重叠。

Answer 2

此外，要更改标题的字体大小，请使用以下代码（改编自 @tonytonov 的答案）：

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)
             ), ...)
}

Answer 3

我更新了@tonytonov 的答案以不干扰默认的 X 轴。它仍然作为轴实现，但实现了自己的“标题”比例，并将用户提供的标题属性（如字体大小和颜色）与使轴不可见所需的默认属性正确合并。此版本隐藏轴而不假定特定的背景颜色。 函数后面三个例子。

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)))