How to connect pairs of data points in plotly in R

Question

library(plotly)
data <- data.frame(name = c("Ana", "Ana", "Joyce", "Joyce", "Kam", "Kam"),
                   type = c("A", "B", "A", "B", "A", "B"),
                   score1 = c(100, 90, 0, 20, 33, 99),
                   score2 = c(100, 30, 0, 20, 55, 66))
> data
   name type score1 score2
1   Ana    A    100    100
2   Ana    B     90     30
3 Joyce    A      0      0
4 Joyce    B     20     20
5   Kam    A     33     55
6   Kam    B     99     66

I have a dataset where each person has 2 scores for test type A and 2 scores for test type B . I want to connect the test scores for each person with a dashed line.

Here's my code for the plot without the dashed lines:

> plot_ly(data = data,
                       x = ~score1,
                       y = ~score2,
                       hoverinfo = 'text',
                       text = ~I(name),
                       mode = "markers",
                       transforms = list(
                         list(
                           type = 'groupby',
                           groups = data$type,
                           styles = list(
                             list(target = "A", value = list(marker =list(color = 'red'))),
                             list(target = "B", value = list(marker =list(color = 'blue')))
                           )
                         )
                       )) 

The desired output is something like this:

Answer 1

Since you're specifying specific colors in the point plot, it's just going to be easier to create the lines first.

First, for each line segment, you will need a separate trace. There are only three, but I used this method due to its dynamic nature. Your line segments are connected by the data in name , so I used that to control the line trace creation.

plt <- plot_ly()
lapply(1:length(unique(df1$name)), 
       function(j) {
         df2 <- filter(df1, name == unique(df1$name)[j])
         plt <<- plt %>% 
           add_trace(type = "scatter", mode = "lines", data = df2, 
                     x = ~score1, y = ~score2, showlegend = F, hoverinfo = "none",
                     line = list(color = "black", dash = "dash"))
       })

Now that the lines are all documented in plt , let's add that original scatter data to the plot. I've added hovertemplate so that the hover content doesn't include the trace name.

plt %>% 
  add_trace(data = df1, x = ~score1, y = ~score2, hovertext = ~name,
            color = ~type, mode = "markers", showlegend = T,
            hovertemplate = "%{hovertext}<extra></extra>",
            marker = list(color = ifelse(df1$type == "A", "red", "blue")))