如何在 R 中使用 Plotly 在折线图上仅显示一些悬停信息点

Question

I have traffic and article dfs as follows:

library(plotly)
library(dplyr)

set.seed(101)
traffic <- data.frame(Date = seq(as.Date("2021-06-01"), as.Date("2021-07-10"), by="days"),
                      Views = round(rnorm(40, 5000, 200),0))

articleData <- data.frame(Date = as.Date(c("2021-06-01", "2021-07-04", "2021-07-10")),
                          article = c("Article 1", "Article 2", "Article 3"))

joinedData <- left_join(traffic, articleData)

I want to make a plotly line graph that shows a line for traffic, but for the 3 dates where there were articles published I would like to add a dot that the person can cover over and it will show what article was published that day. Below is what I was able to put together:

plot_ly(data = joinedData, x = ~Date, y = ~Views, type = "scatter", mode = "lines") %>%
  add_trace(hoverinfo = "text", text = ~article, mode = "markers")

This technically works, but it puts a marker on every single day, not just the 3 days that had articles. Is there a way to ignore marking the days that don't have articles? I really just want to draw attention to the days that have articles published and show whether that article shows a spike in traffic or not.

Answer 1

I think you were really close in your question. I think you just need to filter your data for those three articles and create a new dataframe. You can use the new dataset in add_trace. This will only put points on the dates that had articles published.

library(dplyr)
library(plotly)
filteredJoinedData <- joinedData %>%
  filter(article != "NA")

plot_ly(data = joinedData, x = ~Date, y = ~Views, type = "scatter", mode = "lines") %>%
  add_trace(data = filteredJoinedData, hoverinfo = "text", text = ~article, mode = "markers")

Giving you this graph