trivial shiny app with file download handler

app.R

library(shiny)
library(dplyr)

server <- function(input, output) {

    output$downloadData <- downloadHandler(
        
        filename = function() {
            paste('data_', Sys.Date(), '.csv', sep='')
        },
        content = function(file) {
            
                mtcars %>%
                filter(am == input$trans) %>%
                group_by(Cylinder = factor(cyl)) %>%
                summarise(Mean.HP = mean(hp)) %>%
                write.csv(file, row.names = FALSE)
            
         }
    )

    output$dattable <- DT::renderDataTable(
        
            mtcars %>%
            filter(am == input$trans) %>%
            group_by(Cylinder = factor(cyl)) %>%
            summarise(Mean.HP = mean(hp))
    )

}

ui <- fluidPage(
    sidebarLayout(
        sidebarPanel(
           selectInput("trans", "Transmission", choices = c(0,1))
        ),
        mainPanel(
            downloadButton("downloadData", "Download Your 'Clean' Data"),
            DT::dataTableOutput("dattable")
    )
)
)

shinyApp(ui = ui, server = server)