Interactive data point selection with ggplotly/plotly charts

eventdata.R

## Interactive data point selection with ggplotly/plotly charts, return selected key to variable
## Load required packages
library(plotly)
library(ggplot2)
library(shiny)

## Defining a key column in mtcars which will be used for event handling in event_data()
row.names(mtcars) <- gsub(' ','.',row.names(mtcars))
mtcars$key <- row.names(mtcars)

### Ui code begins below
ui <- fluidPage(
  h1("Demo - Interactive data point selection with ggplotly/plotly charts"),
  h4("Subset the dataset using the data points selected from the chart. Drag and select one or multi data points"),
  br(),
  ## Plotly plot display
  plotlyOutput("plot"),
  
  ## Data point information display post click
  verbatimTextOutput("click")
)


## Server side code begins below
server <- function(input, output, session) {
  
  ## ggplotly scatter plot
  output$plot <- renderPlotly({
    
    myplot <- ggplot(mtcars, aes(x = mpg, 
                            y = wt, 
                            key = key)) + geom_point()
    ## in above code line, use the argument key inside ggplot which will be used for event handling
    ggplotly(myplot) %>% 
      layout(dragmode = "select")
    
  })
  
  ## returns the data related to data points selected by the user
  output$click <- renderPrint({

    
    ## Click_data will have the keys (row identifiers) corresponding to selected data points
    click_data <- event_data("plotly_selected")

    ## Event mode options. There are many more to experiment
    ## plotly_click - click on one data point
    ##  Plotly_selected - multi point select
        
    if(is.null(click_data)) 
      "No data points selected on scatter plot..." 
    else 
      mykey <<- renderText(click_data$key)
      filter(mtcars, key %in% click_data$key) %>% select(-key)
    ## Subsetting in above step based on selected data points and removing the key column
    
  })
}
shinyApp(ui, server)
mykey <- unlist(strsplit(mykey(),' '))