plotlyclicklasso.R

# Clicking on a single point seems to clear the lasso selection. But the opposite is not true: doing a lasso selection still keeps the clicked point information.
# To reproduce:
# - Click a single point
# - Do a lasso selection
# - Both are currently visible
# - Click a different point
# - Now the lasso selection information is gone
# - Do a lasso selection again, both are visible again

library(shiny)
library(plotly)

ui <- fluidPage(
  plotlyOutput("plot"),
  verbatimTextOutput("click"),
  verbatimTextOutput("brush")
)

server <- function(input, output, session) {
  
  nms <- row.names(mtcars)
  
  output$plot <- renderPlotly({
    p <- ggplot(mtcars, aes(x = mpg, y = wt, key = nms)) + geom_point()
    ggplotly(p) %>% layout(dragmode = "lasso")
  })
  
  output$click <- renderPrint({
    d <- event_data("plotly_click")
    if (!is.null(d)) d
  })
  
  output$brush <- renderPrint({
    d <- event_data("plotly_selected")
    if (!is.null(d)) d
  })
  
}

shinyApp(ui, server)

Ideally I'd want to do this directly using plotly, not by having to use reactiveValues to store the previous selections. I want to know if plotly itself has a way to not clear the lasso selection, just like it doesn't clear the clicked point

Whenever I've needed to maintain state like this I use a observeEvent(event_data(...), { modify reactiveValues() here }) pattern https://github.com/ropenscilabs/eechidna/blob/a9213ae14d082c9baa5c64f77c021f37dcbb417d/R/app.R#L213-L253