如何在R中的plotly线图中添加图例？

Question

I am trying to add legend for each line in a grouped line plot in plotly but I cannot find the relevant documentation. Here is the code without the legends (code from the official documentation https://plot.ly/r/group-by/ ).

library(plotly)

p <- plot_ly(
  type = 'scatter',
  x = mtcars$hp,
  y = mtcars$qsec,
  text = paste("Make: ", rownames(mtcars),
               "<br>hp: ", mtcars$hp,
               "<br>qsec: ", mtcars$qsec,
               "<br>Cyl: ", mtcars$cyl),
  hoverinfo = 'text',
  mode = 'markers',
  transforms = list(
    list(
      type = 'groupby',
      groups = mtcars$cyl,
      styles = list(
        list(target = 4, value = list(line =list(color = 'blue'))),
        list(target = 6, value = list(line =list(color = 'red'))),
        list(target = 8, value = list(line =list(color = 'black')))
      )
      )
    )
  )

Answer 1

Adding a layout command at the bottom will work layout(showlegend = TRUE) . This can work by being piped in using the library(dplyr) package as shown here:

library(plotly)
library(dplyr)

p <- plot_ly(
  type = 'scatter',
  x = mtcars$hp,
  y = mtcars$qsec,
  text = paste("Make: ", rownames(mtcars),
               "<br>hp: ", mtcars$hp,
               "<br>qsec: ", mtcars$qsec,
               "<br>Cyl: ", mtcars$cyl),
  hoverinfo = 'text',
  mode = 'markers',
  transforms = list(
    list(
      type = 'groupby',
      groups = mtcars$cyl,
      styles = list(
        list(target = 4, value = list(line =list(color = 'blue'))),
        list(target = 6, value = list(line =list(color = 'red'))),
        list(target = 8, value = list(line =list(color = 'black')))
      )
      )
    )
  ) %>%
layout(showlegend = TRUE)