r - 在ggvis图表下方添加水平离散图例

Question

我想在 ggvis 下面做一个水平图例图表。我可以使用图例属性将其放置在图表下方，但不知道如何将标签水平放置在图例标题下方。下面是最小的可重现代码(从网上抓取)。

df1 = data.frame(x=sample(1:10), y=sample(1:10))
df2 = data.frame(x=1:10, y=1:10)
df3 = data.frame(x=1:10, y=sqrt(1:10))

df2$id <- 1
df3$id <- 2
df4    <- rbind(df2,df3)
df4$id <- factor(df4$id)

df4 %>% ggvis(x=~x, y=~y, stroke=~id) %>% layer_lines() %>%
    # make sure you use add relative scales
    add_relative_scales() %>%
    # values for x and y need to be between 0 and 1
    # e.g for the x-axis 0 is the at far-most left point and 1 at the far-right 
    add_legend("stroke", title="Cylinders",
               properties=legend_props(
                   legend=list(
                       x=scaled_value("x_rel", 0.2),
                       y=scaled_value("y_rel", -.2)
                   ))) %>%
    layer_points(x=~x, y=~y, data=df1, stroke:='black') 

Answer 1

这肯定是一个黑客，但效果很好:

df4 %>% ggvis(x=~x,y=~y,stroke=~id) %>% layer_lines() %>%
  #make sure you use add relative scales
  add_relative_scales() %>%
  #values for x and y need to be between 0 and 1
  #e.g for the x-axis 0 is the at far-most left point and 1 at the far-right 
  add_legend("stroke", title = "Cylinders", values = c(1, 1),
             properties = legend_props(
               legend = list(
                 x = scaled_value("x_rel", 0.2),
                 y = scaled_value("y_rel", -.2)
               ))) %>%
  add_legend("stroke", title = " ", values = c(2, 2),
             properties = legend_props(
               legend = list(
                 x = scaled_value("x_rel", 0.23),
                 y = scaled_value("y_rel", -.2)
               ))) %>%
  layer_points(x=~x,y=~y,data = df1,stroke:='black') 

基本上，我正在添加另一个 add_legend ，设置标题为空，调整 scale_value因此它非常接近第一个图例但不重叠。然后我用 values = c(1,1) 设置第一个图例第二个是 values = c(2,2)以便两个值堆叠在一起。这使它看起来像一个具有水平值的图例。