Conditionally coloring segments in plotly incorrectly rendering in legend when turned off-CodePudding

I have a function which generates a plot in which the user can specify whether to color the line segments according to a grouping variable:

## libraries
library(tidyverse)
library(plotly)

## data
df <- data.frame(grp = c("a", "b"),
                 val_start = c(1, 2),
                 val_end = c(5, 6))

df_long <- df %>% 
  pivot_longer(cols = -grp, names_to = "metric", values_to = "val")

## function
plot_func <- function(plot_color) {
  ## create main plot object
  plot_obj <- df %>% 
    plot_ly()
  ## generate colored/non-colored segments depending on user selection
  if(plot_color == T) {
    plot_obj <- plot_obj %>% 
      add_segments(x = ~val_start,
                   xend = ~val_end,
                   y = ~grp,
                   yend = ~grp,
                   color = ~grp,
                   colors = c("a" = "red", "b" = "blue"))
  } else  {
    plot_obj <- plot_obj %>% 
      add_segments(x = ~val_start,
                   xend = ~val_end,
                   y = ~grp,
                   yend = ~grp)
  }
  ## generate primary colors
  plot_obj %>% 
    add_markers(inherit = F,
                data = df_long,
                x = ~val,
                y = ~grp,
                showlegend = F,
                marker = list(color = "green")) %>% 
    ## generate goal marker
    add_markers(name = "goal",
                x = 4,
                y = ~grp,
                marker = list(color = "black"))
}

As shown below, the function works correctly when the user choses to color the plot:

## render plot
plot_func(plot_color = T)

However, when the user choses not to color the plot, the function annoyingly generates a legend trace for the non-colored line, where all I would like to be shown is the goal marker legend.

## render plot
plot_func(plot_color = F)

Does anyone know how to fix this? I've tried specifying showlegend = T or showlegend = F in each of the respective traces, but when I do that, the legend appears when color is turned on, but then disappears completely when color is turned off.

CodePudding user response：

You need to "globally" activate showlegend via layout(showlegend = T) for your plot_obj:

## libraries
library(tidyr)
library(plotly)

## data
df <- data.frame(grp = c("a", "b"),
                 val_start = c(1, 2),
                 val_end = c(5, 6))

df_long <- df %>% 
  pivot_longer(cols = -grp, names_to = "metric", values_to = "val")

## function
plot_func <- function(plot_color) {
  ## create main plot object
  plot_obj <- df %>% 
    plot_ly() %>% layout(showlegend = T)
  ## generate colored/non-colored segments depending on user selection
  if(plot_color == T) {
    plot_obj <- plot_obj %>% 
      add_segments(x = ~val_start,
                   xend = ~val_end,
                   y = ~grp,
                   yend = ~grp,
                   color = ~grp,
                   colors = c("a" = "red", "b" = "blue"))
  } else  {
    plot_obj <- plot_obj %>% 
      add_segments(x = ~val_start,
                   xend = ~val_end,
                   y = ~grp,
                   yend = ~grp,
                   showlegend = F)
  }
  ## generate primary colors
  plot_obj %>% 
    add_markers(inherit = F,
                data = df_long,
                x = ~val,
                y = ~grp,
                showlegend = F,
                marker = list(color = "green")) %>% 
    ## generate goal marker
    add_markers(name = "goal",
                x = 4,
                y = ~grp,
                marker = list(color = "black"))
}

plot_func(plot_color = F)