See https://github.com/plotly/dashR/issues/182#issuecomment-591553051

app.R

library(dash)
library(dashCoreComponents)
library(dashHtmlComponents)
library(plotly)
#library(jsonlite)

app <- Dash$new()

app$layout(
  htmlDiv(
    list(
      htmlDiv(id='my-div', children = "Dash: A web application framework for R."),
      dccGraph(
        id='sepal_len2petal_len',
        figure=plot_ly(data = iris, x = ~Sepal.Length, y = ~Petal.Length)
      ),
      dccGraph(
        id='sepal_len2sepal_wid',
        figure=plot_ly(data = iris, x = ~Sepal.Length, y = ~Sepal.Width)
      ),
      dccGraph(
        id='petal_len2petal_wid',
        figure=plot_ly(data = iris, x = ~Petal.Length, y = ~Petal.Width)
      )
    )
  )
)

app$callback(
  #output=list(id='my-div', property='children'),
  output=list(id='sepal_len2sepal_wid', property='figure'),
  params=list(input(id = 'sepal_len2petal_len', property = 'selectedData')),
  function(selectedData) {
    #save(selectedData, file = "selectedData.RData")
    xs <- unlist(lapply(selectedData$points, function(sdata){
      sdata$x
    }))
    ys <- unlist(lapply(selectedData$points, function(sdata){
      sdata$y
    }))
    target <- unlist(lapply(seq_along(xs), function(x){
      intersect(
        which(iris[,1] == xs[x]),
        which(iris[,3] == ys[x]))
    }))
    target <- sort(unique(target))
    new_iris = iris[target, ]
    
    return(plot_ly(data = new_iris, x = ~Sepal.Length, y = ~Sepal.Width))
    
    #print(selectedData)
#    return(plot_ly(data = new_iris, x = ~Sepal.Length, y = ~Sepal.Width))
#    return(prettify(toJSON(selectedData),indent = 2))
  })

# When you run this in the remote server
#app$run_server(host="0.0.0.0")

# When you run this in the local server
print(app$server$port)
app$run_server()