R Plotly - Add annotation to reference line in a scatter plot

Question

I have created a scatterplot with Plotly in R using the iris dataset and have added two reference lines, one on the x-axis denoting the mean Sepal.Width and the other on the y-axis denoting the mean Sepal.Length.

Below is the executable R code:

library(dplyr)
library(plotly) 

iris <- datasets::iris

scatterplot <- plot_ly(data = iris, x = ~Sepal.Width, y = ~Sepal.Length, type = 'scatter',
                       text = ~Species,
                       color = I('orange')) %>%
               layout(shapes=list(list(type = 'line', 
                                     x0 = mean(iris$Sepal.Width), 
                                     x1 = mean(iris$Sepal.Width),
                                     y0 = 4, 
                                     y1 = 8, 
                                     line = list(width = 2)),
                                list(type = 'line', 
                                     x0 = 1.5, 
                                     x1 = 5, 
                                     y0 = mean(iris$Sepal.Length), 
                                     y1 = mean(iris$Sepal.Length), 
                                     line = list(width = 2))))

scatterplot

The above R code produces the following Plotly output

I want to add annotation text (ie label) for the two reference lines ("Mean Sepal Width" and "Mean Sepal Length").

I came across a similar post however the solution mentioned there did not work for me. If someone can provide me the solution with the code then that would be highly appreciated.

PS: I am using Plotly version 4.8.0

Answer 1

The following code solved my problem. Hope it helps someone.

library(dplyr)
library(plotly)

iris <- datasets::iris

scatter <- plot_ly(data = iris, x = ~Sepal.Width, y = ~Sepal.Length, type = 'scatter',
                   text = ~Species,
                   color = I('orange')) %>%
              layout(shapes=list(list(type = 'line', 
                                        x0 = mean(iris$Sepal.Width), 
                                        x1 = mean(iris$Sepal.Width),
                                        y0 = 4, 
                                        y1 = 8, 
                                        line = list(width = 2)),
                                  list(type = 'line', 
                                        x0 = 1.5, 
                                        x1 = 5, 
                                        y0 = mean(iris$Sepal.Length), 
                                        y1 = mean(iris$Sepal.Length), 
                                        line = list(width = 2))), 
                                  annotations = list(list( 
                                            x = 3.4,
                                            y = 7.9,
                                            xref = 'x',
                                            yref = 'y',
                                            text = 'Mean Sepal Width',
                                            showarrow = FALSE
                                          ),
                                            list( 
                                              x = 4.7,
                                              y = 5.6,
                                              xref = 'x',
                                              yref = 'y',
                                              text = 'Mean Sepal Length',
                                              showarrow = FALSE
                                            )))      
scatter