Leaflet map responsive to csv fileInput in Shiny

Question

I have a simple shiny app that plots points from a csv file input. Currently, when I upload the file to the shiny app, the map doesn't do anything. I think this is because the leaflet map isn't reacting to the file being uploaded. How might I be able to fix this?

See my code below. Sample data can be found HERE.

library(shiny)
library(shinydashboard)
library(leaflet)
library(dplyr)
library(htmltools)

shinyApp(
  ui <- fluidPage(

    titlePanel("eBird Visualizer"),
    fileInput("MyEBirdData_in", "MyEBirdData", buttonLabel = "Upload a .csv", 
              placeholder = "No File Selected...", width = "255px", 
              accept = ".csv"),
    leafletOutput("myMap")
  ),

  server = function(input, output) {

    output$contents <- renderTable({

      inFile <- input$MyEBirdData_in
      if (is.null(inFile))
        return(NULL)
      myData = read.csv(inFile$datapath, header = input$header)

      df0 = data.frame(myData$Submission.ID, myData$Latitude, myData$Longitude)
      df = unique(df0)
      names(df)[2] = 'latitude'
      names(df)[3] = 'longitude'

    })

    output$myMap = renderLeaflet({

      leaflet(data = df) %>% addProviderTiles(providers$CartoDB.Positron)
    })
  }
)

Florian Florian · Accepted Answer · 2017-12-22T09:51:14

renderTable is used to create a reactive table to be displayed in the UI. What you want is to have a variable that can be used in other reactive expressions to trigger them to update, in that case you should use reactive or reactiveValue, see for example here; 2/3 down the page, where they first introduce reactive for a good example.

Also, you are currently referring to input$header, which is not defined. Therefore you get an error when uploading the csv.

So you could do something like this:

library(shiny)
library(shinydashboard)
library(leaflet)
library(dplyr)
library(htmltools)

shinyApp(
  ui <- fluidPage(

    titlePanel("eBird Visualizer"),
    fileInput("MyEBirdData_in", "MyEBirdData", buttonLabel = "Upload a .csv", 
              placeholder = "No File Selected...", width = "255px", 
              accept = c(".csv","text/csv")),
    leafletOutput("myMap")
  ),

  server = function(input, output) {

    my_table <- reactive({

      inFile <- input$MyEBirdData_in
      if (is.null(inFile))
        return(NULL)

      myData = read.csv(inFile$datapath)

      df0 = data.frame(myData$Submission.ID, myData$Latitude, myData$Longitude)
      df = unique(df0)
      names(df)[2] = 'latitude'
      names(df)[3] = 'longitude'
      print(df)
      return(df)
    })

    output$myMap = renderLeaflet({
      if(is.null(my_table()))
      {
        return(leaflet()  %>% addProviderTiles(providers$CartoDB.Positron))
      }
      else
      {
        leaflet(data = my_table()) %>% addProviderTiles(providers$CartoDB.Positron) %>% addMarkers()
      }
    })
  }
)

Leaflet map responsive to csv fileInput in Shiny

1 Answers