Example of using shiny to allow a user to build several plots interactively and iteratively add them as slides of a ppt deck download

shiny_ppt_builder.R

library(shiny)
library(magrittr)
library(ggplot2)
library(officer)

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      sliderInput("obs", "Number of observations:", min = 10, max = 500, value = 100),
      actionButton("add_plot", "Add to ppt"),
      downloadButton("download", "Download PPT")
    ),
    mainPanel(plotOutput("distPlot"))
  )
)

server <- function(input, output) {
  
  # reactive plot controlled by user inputs
  current_plot <- reactive({
    ggplot() + geom_histogram(aes(x = rnorm(input$obs)))
  })
  
  # render the current plot in shiny
  output$distPlot <- renderPlot({
    current_plot()
  })
  
  # create empty reactive list to store plots when user adds them
  plot_list <- reactiveValues()
  
  # when the add plot button is clicked, add the current plot to the reactive list
  observeEvent(input$add_plot, {
    plot_num <- paste0("plot_", input$add_plot)
    plot_list[[plot_num]] <- current_plot() + labs(title = plot_num)
  })
  
  # when download button is clicked...
  output$download <- downloadHandler(
    filename = function() {
      paste("ppt-download-", Sys.Date(), ".pptx", sep="")
    },
    content = function(file) {
      
      # create a deck and add a title slide
      mypres <- read_pptx() %>% 
        add_slide(layout="Title Slide", master="Office Theme") %>%
        ph_with(value = "Hello world", location = ph_location_type(type = "ctrTitle")) %>% 
        ph_with(value = "Example of programmatically adding slides to deck with shiny", location = ph_location_type(type = "subTitle"))
      
      # convert reactive plot list to normal list
      plots <- reactiveValuesToList(plot_list)
      
      # loop over each plot, adding it to a new slide in the deck
      # the double arrow assignment allows for modifying an object outside of the 
      # environment the for loop is run in
      for (i in seq_along(plots)) {
        mypres <<- mypres %>% 
          add_slide(layout = "Title and Content", master = "Office Theme") %>% 
          ph_with(value = plots[[i]], location = ph_location_fullsize())
      }
      
      # download the deck
      mypres %>%
        print(target = file) %>% 
        invisible()
    }
  )
}

shinyApp(ui = ui, server = server)