MWE

library(ggplot2)
library(plotly)

ggplotly(
  ggplot(data=mtcars,
         aes(x=mpg, y=cyl, color=qsec))  
    geom_point()
)

CodePudding user response：

This is only a partial answer; you can change the shape and text of the legend while maintaining its gradient by using a combination of scale_color_continuous and guides(color = guide_legend()), but this will only show up as a ggplot object. For some reason, the legend disappears when you add the plot to ggplotly(), the legend disappears. I suspect that arguments specific to the legend

All of that code in one chunk:

library(tidyverse)
library(plotly)
# original plot
plt <- ggplotly(
  ggplot(data=mtcars,
         aes(x=mpg, y=cyl, color=qsec))  
    geom_point()
)
g <- ggplot(data=mtcars,
            aes(x=mpg, y=cyl, color=qsec))  
  geom_point()
# color by qsec values frame
colByVal <- cbind(ggplot_build(g)$data[[1]], mtcars) %>% 
  as.data.frame() %>% 
  select(colour, qsec) %>% arrange(qsec) %>% 
  group_by(colour) %>% 
  summarise(qsec = median(qsec)) %>% as.data.frame()

parts <- summary(colByVal$qsec)
# drop the mean or median (the same color probably)
parts <- parts[-4]

vals <- lapply(parts, function(k) {
  DescTools::Closest(colByVal$qsec, k)[1]
}) %>% unlist(use.names = F)

cols <- colByVal %>% 
  filter(qsec %in% vals) %>% select(colour) %>% 
  unlist(use.names = F)

ys <- seq(from = .7, by = .07, length.out = length(cols))

# create shapes
shp <- function(y, cr) { # y0, and fillcolor
  list(type = "circle",
       xref = "paper", x0 = 1.1, x1 = 1.125,
       yref = "paper", y0 = y, y1 = y   .025,
       fillcolor = cr, yanchor = "center",
       line = list(color = cr))
}
# create labels
ano <- function(ya, lab) { # y and label
  list(x = 1.13, y = ya   .035, text = lab, 
       xref = "paper", yref = "paper", 
       xanchor = "left", yanchor = 'top', 
       showarrow = F)
}
# the shapes list
shps <- lapply(1:length(cols),
               function(j) {
                 shp(ys[j], cols[j])
               })
# the labels list
labs <- lapply(1:length(cols),
               function(i) {
                 ano(ys[i], as.character(vals[i]))
               })
# ggplot > ggplotly adds an empty shape; this conflicts with calling it in
#   layout(); we'll replace 'shapes' first
plt$x$layout$shapes <- shps
plt %>% hide_colorbar() %>% 
  layout(annotations = labs, showlegend = F, 
         margin = list(t = 30, r = 100, l = 50, b = 30, pad = 3))