README.md

Minimal R shiny app demonstrating:

1. how to upload a CSV file into an R/shiny app
2. how to automatically populate list selectors based on column headers
3. how to use optional list selectors
4. how to populate a list selector with column names of numerical columns only
5. how to use an action button to trigger an event when you're ready to do so

---

Download and install:

• R
• RStudio
• Download the dummy csv file from this gist ( https://gist.github.com/psychemedia/9690079 )

In RStudio run:

install.packages("shiny")

then

library(shiny)

followed by

runGist(9737637)

dummy.csv

fromble,toble,amountify
"London, UK","Cambridge,UK"
"Cambridge,UK","Paris, France",17
"Paris,France","New York,US",24
"Sydney, Australia","Cape Town, South Africa",12	

global.R

##This should detect and install missing packages before loading them - hopefully!

list.of.packages <- c("shiny","ggmap")
new.packages <- list.of.packages[!(list.of.packages %in% installed.packages()[,"Package"])]
if(length(new.packages)) install.packages(new.packages)
lapply(list.of.packages,function(x){library(x,character.only=TRUE)}) 

server.R

shinyServer(function(input, output) {
  
  #This function is repsonsible for loading in the selected file
  filedata <- reactive({
    infile <- input$datafile
    if (is.null(infile)) {
      # User has not uploaded a file yet
      return(NULL)
    }
    read.csv(infile$datapath)
  })
  
 
  #The following set of functions populate the column selectors
  output$toCol <- renderUI({
    df <-filedata()
    if (is.null(df)) return(NULL)
    
    items=names(df)
    names(items)=items
    selectInput("to", "To:",items)
    
  })
  
  output$fromCol <- renderUI({
    df <-filedata()
    if (is.null(df)) return(NULL)
    
    items=names(df)
    names(items)=items
    selectInput("from", "From:",items)
    
  })
  
  #The checkbox selector is used to determine whether we want an optional column
  output$amountflag <- renderUI({
    df <-filedata()
    if (is.null(df)) return(NULL)
    
    checkboxInput("amountflag", "Use values?", FALSE)
  })
  
  #If we do want the optional column, this is where it gets created
  output$amountCol <- renderUI({
    df <-filedata()
    if (is.null(df)) return(NULL)
    #Let's only show numeric columns
    nums <- sapply(df, is.numeric)
    items=names(nums[nums])
    names(items)=items
    selectInput("amount", "Amount:",items)
  })
  
  #This previews the CSV data file
  output$filetable <- renderTable({
    filedata()
  })
  
  #This function is the one that is triggered when the action button is pressed
  #The function is a geocoder from the ggmap package that uses Google maps geocoder to geocode selected locations
  geodata <- reactive({
    if (input$getgeo == 0) return(NULL)
    df=filedata()
    if (is.null(df)) return(NULL)
    
    #The function acts reactively when one of the variables it uses is changed
    #If we don't want to trigger when particular variables change, we need to isolate them 
    isolate({
      #Get the CSV file data
      dummy=filedata()
      #Which from/to columns did the user select?
      fr=input$from
      to=input$to
      #If locations are duplicated in from/to columns, dedupe so we don't geocode same location more than once
      locs=data.frame(place=unique(c(as.vector(dummy[[fr]]),as.vector(dummy[[to]]))),stringsAsFactors=F)
      #Run the geocoder against each location, then transpose and bind the results into a dataframe
      cbind(locs, t(sapply(locs$place,geocode, USE.NAMES=F))) 
    })
    
  })
  
  #This reactive function is essentially chained on the previous one
  geodata2 <- reactive({
    if (input$getgeo == 0) return(NULL)
    df=filedata()
    if (input$amountflag != 0) {
      maxval=max(df[input$amount],na.rm=T)
      minval=min(df[input$amount],na.rm=T)
      df$b8g43bds=10*df[input$amount]/maxval
    }
    gf=geodata()
    df=merge(df,gf,by.x=input$from,by.y='place')
    merge(df,gf,by.x=input$to,by.y='place')
  })
  
  output$geotable <- renderTable({
    if (input$getgeo == 0) return(NULL)
    geodata2()
  })
  
})

ui.R

shinyUI(pageWithSidebar(
  headerPanel("CSV File Upload Demo"),
  
  sidebarPanel(
    #Selector for file upload
    fileInput('datafile', 'Choose CSV file',
              accept=c('text/csv', 'text/comma-separated-values,text/plain')),
    #These column selectors are dynamically created when the file is loaded
    uiOutput("fromCol"),
    uiOutput("toCol"),
    uiOutput("amountflag"),
    #The conditional panel is triggered by the preceding checkbox
    conditionalPanel(
      condition="input.amountflag==true",
      uiOutput("amountCol")
    ),
    #The action button prevents an action firing before we're ready
    actionButton("getgeo", "Get geodata")
    
  ),
  mainPanel(
    tableOutput("filetable"),
    tableOutput("geotable")
  )
))