Uploading and dowloading data in RShiny - Answer Key

Exercise 1

Lets add a layout to the R Shiny app from the exercise in the previous lesson. That app should look like:

library(shiny)
library(DT)
library(tidyverse)

# User Interface
ui <- fluidPage(
  # Upload the file
  fileInput("input_file", "Upload file"),
  # Select from the dropdown menu the column you want on the x-axis
  selectInput("x_axis_input", "Select x-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")),
  # Select from the dropdown menu the column you want on the y-axis
  selectInput("y_axis_input", "Select y-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")),
  # The output plot
  plotOutput("plot"),
  # The download plot button
  downloadButton("download_button", "Download the data .png")
)

# Server
server <- function(input, output) {
  # Reactive expression to hold the uploaded data 
  iris_data <- reactive({
    req(input$input_file)
    read.csv(input$input_file$datapath)
  })
  # Reactive expression to create a scatterplot from the uploaded data and user selected axes
  iris_plot <- reactive ({
  ggplot(iris_data()) +
    geom_point(aes_string(x = input$x_axis_input, y = input$y_axis_input))
  })
  # Render the plot from the iris_plot() reactive expression
  output$plot <- renderPlot({
    iris_plot()
  })
  # Download the data
  output$download_button <- downloadHandler(
    # The placeholder name for the file will be called iris_plot.png
    filename = function() {
      "iris_plot.png"
    },
    # The content of the file will be the contents of the iris_plot() reactive expression
    content = function(file) {
      png(file)
      print(iris_plot())
      dev.off()
    }
  )
}

# Run the app
shinyApp(ui = ui, server = server)

We are going to try to create an app that looks like:

1. Place the fileInput() and selectInput()s within a sidebar with the plot in the mainPanel(). Underneath the sidepanelLayout(), place a themetic break and underneath that place a right-aligned downloadButton().

# Load libraries and data
library(shiny)
library(tidyverse)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      # Upload the file
      fileInput("input_file", "Upload file"),
      # Select from the dropdown menu the column you want on the x-axis
      selectInput("x_axis_input", "Select x-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")),
      # Select from the dropdown menu the column you want on the y-axis
      selectInput("y_axis_input", "Select y-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width"))
    ),
    mainPanel(
      # The output plot
      plotOutput("plot")
    )
  ),
  hr(),
  fluidRow(
    column(12,
           align = "right",
           # The download plot button
           downloadButton("download_button", "Download the data .png")
    )
  )
)

# Server
server <- function(input, output) {
  # Reactive expression to hold the uploaded data 
  iris_data <- reactive({
    req(input$input_file)
    read.csv(input$input_file$datapath)
  })
  # Reactive expression to create a scatterplot from the uploaded data and user selected axes
  iris_plot <- reactive ({
    ggplot(iris_data()) +
      geom_point(aes_string(x = input$x_axis_input, y = input$y_axis_input))
  })
  # Render the plot from the iris_plot() reactive expression
  output$plot <- renderPlot({
    iris_plot()
  })
  # Download the data
  output$download_button <- downloadHandler(
    # The placeholder name for the file will be called iris_plot.png
    filename = function() {
      "iris_plot.png"
    },
    # The content of the file will be the contents of the iris_plot() reactive expression
    content = function(file) {
      png(file)
      print(iris_plot())
      dev.off()
    }
  )
}

# Run the app
shinyApp(ui = ui, server = server)

2. Add the "superhero" theme from shinythemes to the app.

Hint: Be sure to add library(shinythemes) and make sure it is loaded.

# Load libraries and data
library(shiny)
library(tidyverse)
library(shinythemes)

ui <- fluidPage(theme = shinytheme("superhero"),
                ...
)

The final app should look like:

# Load libraries and data
library(shiny)
library(tidyverse)
library(shinythemes)

ui <- fluidPage(theme = shinytheme("superhero"),
  sidebarLayout(
    sidebarPanel(
      # Upload the file
      fileInput("input_file", "Upload file"),
      # Select from the dropdown menu the column you want on the x-axis
      selectInput("x_axis_input", "Select x-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")),
      # Select from the dropdown menu the column you want on the y-axis
      selectInput("y_axis_input", "Select y-axis", choices = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width"))
    ),
    mainPanel(
      # The output plot
      plotOutput("plot")
    )
  ),
  hr(),
  fluidRow(
    column(12,
           align = "right",
           # The download plot button
           downloadButton("download_button", "Download the data .png")
    )
  )
)

# Server
server <- function(input, output) {
  # Reactive expression to hold the uploaded data 
  iris_data <- reactive({
    req(input$input_file)
    read.csv(input$input_file$datapath)
  })
  # Reactive expression to create a scatterplot from the uploaded data and user selected axes
  iris_plot <- reactive ({
    ggplot(iris_data()) +
      geom_point(aes_string(x = input$x_axis_input, y = input$y_axis_input))
  })
  # Render the plot from the iris_plot() reactive expression
  output$plot <- renderPlot({
    iris_plot()
  })
  # Download the data
  output$download_button <- downloadHandler(
    # The placeholder name for the file will be called iris_plot.png
    filename = function() {
      "iris_plot.png"
    },
    # The content of the file will be the contents of the iris_plot() reactive expression
    content = function(file) {
      png(file)
      print(iris_plot())
      dev.off()
    }
  )
}

# Run the app
shinyApp(ui = ui, server = server)