Rplotly：如何设置第二个图例组的图例方向？

Question

我知道我可以使用 layout(legend = list(orientation = 'h')) 设置绘图的图例方向。但是，如果我在图中包含第二个图例组，我怎样才能将该图例组的方向设置为水平。这是一个简单的例子。您可以看到第一个图例组是水平的，但第二个图例组是垂直的。谢谢！

library(plotly)
library(dplyr)


d1 <- data.frame(x = rep(seq(1,10), 2), 
                 y = runif(20), 
                 n = c(rep("Entry 1", 10), rep("Entry 2", 10)))
d2 <- data.frame(x = rep(seq(1,10), 4), 
                 y = runif(40), 
                 n = c(rep("Entry A", 10), rep("Entry B", 10),
                       rep("Entry C", 10), rep("Entry D", 10)))

p <- plot_ly()

p <- p %>%
  add_trace(data = d1, type = "scatter", mode = "lines",
            x = ~x, y = ~y, name = ~n)

p <- p %>%
  add_trace(data = d2, type = "bar",
            x = ~x, y = ~y, name = ~n, 
            legendgroup = "group2")

p <- p %>%
  layout(legend = list(orientation = 'h'))
p