How to organize large Shiny apps?
After addition of modules to R shiny. Managing of complex structures in shiny applications has become a lot easier.
Detailed description of shiny modules:Here
Advantages of using modules:
- Once created, they are easily reused
- ID collisions is easier to avoid
- Code organization based on inputs and output of modules
In tab based shiny app, one tab can be considered as one module which has inputs and outputs. Outputs of tabs can be then passed to other tabs as inputs.
Single-file app for tab-based structure which exploits modular thinking. App can be tested by using cars dataset. Parts of the code where copied from the Joe Cheng(first link). All comments are welcome.
# Tab module# This module creates new tab which renders dataTabledataTabUI <- function(id, input, output) { # Create a namespace function using the provided id ns <- NS(id) tagList(sidebarLayout(sidebarPanel(input), mainPanel(dataTableOutput(output))))}# Tab module# This module creates new tab which renders plotplotTabUI <- function(id, input, output) { # Create a namespace function using the provided id ns <- NS(id) tagList(sidebarLayout(sidebarPanel(input), mainPanel(plotOutput(output))))}dataTab <- function(input, output, session) { # do nothing... # Should there be some logic?}# File input module# This module takes as input csv file and outputs dataframe# Module UI functioncsvFileInput <- function(id, label = "CSV file") { # Create a namespace function using the provided id ns <- NS(id) tagList( fileInput(ns("file"), label), checkboxInput(ns("heading"), "Has heading"), selectInput( ns("quote"), "Quote", c( "None" = "", "Double quote" = "\"", "Single quote" = "'" ) ) )}# Module server functioncsvFile <- function(input, output, session, stringsAsFactors) { # The selected file, if any userFile <- reactive({ # If no file is selected, don't do anything validate(need(input$file, message = FALSE)) input$file }) # The user's data, parsed into a data frame dataframe <- reactive({ read.csv( userFile()$datapath, header = input$heading, quote = input$quote, stringsAsFactors = stringsAsFactors ) }) # We can run observers in here if we want to observe({ msg <- sprintf("File %s was uploaded", userFile()$name) cat(msg, "\n") }) # Return the reactive that yields the data frame return(dataframe)}basicPlotUI <- function(id) { ns <- NS(id) uiOutput(ns("controls"))}# Functionality for dataselection for plot# SelectInput is rendered dynamically based on databasicPlot <- function(input, output, session, data) { output$controls <- renderUI({ ns <- session$ns selectInput(ns("col"), "Columns", names(data), multiple = TRUE) }) return(reactive({ validate(need(input$col, FALSE)) data[, input$col] }))}################################################################################### Here starts main program. Lines above can be sourced: source("path-to-module.R")##################################################################################library(shiny)ui <- shinyUI(navbarPage( "My Application", tabPanel("File upload", dataTabUI( "tab1", csvFileInput("datafile", "User data (.csv format)"), "table" )), tabPanel("Plot", plotTabUI( "tab2", basicPlotUI("plot1"), "plotOutput" ))))server <- function(input, output, session) { datafile <- callModule(csvFile, "datafile", stringsAsFactors = FALSE) output$table <- renderDataTable({ datafile() }) plotData <- callModule(basicPlot, "plot1", datafile()) output$plotOutput <- renderPlot({ plot(plotData()) })}shinyApp(ui, server)
I really like how Matt Leonawicz organises his apps. I took his approach learning how to use Shiny, as we all know it can get quite scattered if not properly managed. Have a look at his structure, he gives an overview of the way he organises the apps in the app called run_alfresco
I wrote Radiant. I have not heard people say bad things about the code organization (yet) but I am sure it could be better. One option would be to separate the ui and logic as Joe Cheng does in shiny-partials.
https://github.com/jcheng5/shiny-partials
Another might be to try OO programming, e.g., using R6 http://rpubs.com/wch/17459