Add specific legend to R plotly chart

Question

Does someone know how if it is possible to add the following kind of legend to a R plot_ly chart ?

Please find a reproductible example below

In this example, bar colors depends on velocity value: I would like to print the legend as mentionned above and not only get "trace 0" ...

library(plotly)
library(data.table)

example_data <- data.table(x = c(1,2,3,4,5,6), y = c(7,9,4,3,8,9), velocity = c(0.6,1.4,5,4,0.2,1.1))
example_data$color <- cut(example_data$velocity,breaks = c(0,0.8,1.2,1.5,10),labels = c("lightgreen","darkgreen","yellow","red"))

plot_ly(data = example_data, x = ~ x,y =  ~y ,color =  ~ I(color),type = "bar") %>% 
  layout(showlegend = TRUE)

Thanks a lot !

Answer 1

You can create a new column with the names for the legend. And reorder the factor to be from low (0 - 0.8) to high (> 1.5).

You can try this:

example_data <- data.table(x = c(1,2,3,4,5,6), y = c(7,9,4,3,8,9), velocity = c(0.6, 1.4, 5, 4, 0.2, 1.1), 
                           name = c("0 - 0.8", "1.2 - 1.5", " >1.5", " >1.5", "0 - 0.8", "0.8 - 1.2"))

example_data$name <- as.factor(example_data$name)
example_data$name <- factor(example_data$name, levels = c("0 - 0.8", "0.8 - 1.2", "1.2 - 1.5", " >1.5"))

pal <- c("lightgreen", "darkgreen", "yellow", "red")

plot_ly(data = example_data, x = ~ x,y =  ~y ,color =  ~as.factor(name), colors = ~pal, type = "bar") %>% 
  layout(showlegend = TRUE, legend = list(orientation = "h",
                                          xanchor = "center",  
                                          x = 0.5, y = 7))