A loop around downloadButton in ui.R and around downloadHandler in server.R: is it possible?

[Dimitri Liakhovitski]

Hello!

I have a simple example code that works fine (below). It generates a list of several tiny data frames (reactive object 'myout' in server.R). The number of the data frames is based on user's input.('NumRuns').

My current code allows the user to download the first of these data frames - via downloadButton in ui.R and downloadHandler in server.r.

I am wondering if it's possible to create a loop around both downloadButton and downloadHandler so that - after the analysis is run (actionButton) - the user gets as many buttons to download as there were data frames generated in 'myout'. Is it even possible?

Or maybe it's possible to create one downloadButton that allows the user to 'pick' which data frame s/he wants to download?

Thanks a lot for any hints - because I am not sure how to approach it!

My code (I run it using: runApp(launch.browser = T)

### My ui.R code:

shinyUI(pageWithSidebar(

  

  headerPanel("My App"),

  

  sidebarPanel(

    numericInput('NumRuns','Number of runs',value=3,min=3,max=10,step=1),

    br(),

    actionButton(inputId="goButton","Run!"),

    br(),

    br(),

    textInput("downloadData","Save My Data Frame:",value="Data Frame 1"),

    downloadButton('downloadData','Save my file!')

    

  ),

  

  mainPanel(

    tabsetPanel(

      tabPanel("Shows the 1st data frame",tableOutput("mydf"))

    )

  )

))

### My 'server.R' code:

shinyServer(function(input,output){

  

  

  ### Creating files for displaying and downloading

  

  myout = reactive({

    if(input$goButton==0) return(NULL)

    

    nrruns=input$NumRuns

    mylist=NULL

    for(i in 1:nrruns){

      mylist[[i]]<-data.frame(a=rnorm(10),b=runif(10))

      names(mylist)[i]<-paste("dataframe",i,sep="")

    }

    return(mylist)

  })

  

  # Grabbing only the 1st data frame:

  output$mydf <- renderTable({

    if(input$goButton==0) return(NULL)

    myout()$dataframe1

  })

  

  # Allowing to download only the 1st data frame:

  output$downloadData <- downloadHandler(

    filename = function() { paste(input$downloadData, " ",Sys.Date(),".csv",sep="") },

    content = function(file) {

      write.csv(myout()$dataframe1,file,row.names=F)

    }

  )

  

})

[Joe Cheng]

Yes, this is possible. You'll need to use uiOutput/renderUI to render the buttons, each with a different ID (e.g. downloadData1 through downloadDataN). For defining the download handlers dynamically, use a pattern like:

observe({

  lapply(1:N, function(i) {

    output[[paste0("downloadData", i)]] <- downloadHandler(...)

  })

})

the important thing there being that you can assign to output[[id]] if your output names are dynamic.

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[Dimitri Liakhovitski]

Thank you so much, Joe!

I really don't know much about HTML and don't understand how exactly use uiOutput/renderUI?

I found some examples online, but not sure how to apply them to my case.

Where should I put that observe statement? in "server.R"?

Thank you and sorry for being dumb.

D.

[Joe Cheng]

A single call to uiOutput should go into your ui.R file, where you want the download buttons to all appear. For example, uiOutput("downloadButtons"). Then in server.R, you define an output like so:

output$downloadButtons <- renderUI({

  lapply(1:N, function(i) {

    downloadButton(paste0("downloadData", i), paste0("Download No. ", i))

  })

})

And the observe code should also be right in server.R. Both of these blocks of code should be inside the shinyServer function.

To view this discussion on the web visit https://groups.google.com/d/msgid/shiny-discuss/94c8f5d6-2380-424f-8b70-020c761358ae%40googlegroups.com.

[Dimitri Liakhovitski]

Thanks a lot again, Joe.

In your code it says: "1:N" 

But what is N? I replaced it with input$NumRuns.

However, I am getting an error: 

Error in output$downloadButtons <- renderUI({ : object 'output' not found

Thanks again for your help!

Here is my code:

# For running:

library(shiny)

runApp(launch.browser = T)

# ui.R:

shinyUI(pageWithSidebar(

  

  headerPanel("My App"),

  

  sidebarPanel(

    numericInput('NumRuns','Number of runs',value=3,min=3,max=10,step=1),

    br(),

    actionButton(inputId="goButton","Run!"),

    br(),

    br(),

    output$downloadButtons <- renderUI({

      lapply(1:input$NumRuns, function(i) {

        downloadButton(paste0("downloadData", i), paste0("Download No. ", i))

      })

    })    

  ),

  

  mainPanel(

    tabsetPanel(

      tabPanel("Shows the 1st data frame",tableOutput("mydf"))

    )

  )

))

# server.R:

shinyServer(function(input,output){

  

  

  ### Creating files for displaying and downloading

  

  myout = reactive({

    if(input$goButton==0) return(NULL)

    

    nrruns=input$NumRuns

    mylist=NULL

    for(i in 1:nrruns){

      mylist[[i]]<-data.frame(a=rnorm(10),b=runif(10))

      names(mylist)[i]<-paste("dataframe",i,sep="")

    }

    return(mylist)

  })

  

  # Grabbing only the 1st data frame:

  output$mydf <- renderTable({

    if(input$goButton==0) return(NULL)

    myout()$dataframe1

  })

  

  observe({

    lapply(1:input$NumRuns, function(i) {

      output[[paste0("downloadData", i)]] <- downloadHandler(...)

    })

  })

  

})

[Dimitri Liakhovitski]

I am still struggling with it. Now it says: 

Error in output$downloadButtons <- renderUI({ : object 'output' not found

Help please?

Thank you!

My ui.R code is:

shinyUI(pageWithSidebar(

  

  headerPanel("My App"),

  

  sidebarPanel(

    numericInput('NumRuns','Number of runs',value=3,min=3,max=10,step=1),

    br(),

    actionButton(inputId="goButton","Run!"),

    br(),

    br(),

    output$downloadButtons <- renderUI({

      lapply(1:input$NumRuns, function(i) {

        downloadButton(paste0("downloadData", i), paste0("Download No. ", i))

      })

    })    

  ),

  

  mainPanel(

    tabsetPanel(

      tabPanel("Shows the 1st data frame",tableOutput("mydf"))

    )

  )

))

My "server.R" code is:

shinyServer(function(input,output){

  

  

  ### Creating files for displaying and downloading

  

  myout = reactive({

    if(input$goButton==0) return(NULL)

    

    nrruns=input$NumRuns

    mylist=NULL

    for(i in 1:nrruns){

      mylist[[i]]<-data.frame(a=rnorm(10),b=runif(10))

      names(mylist)[i]<-paste("dataframe",i,sep="")

    }

    return(mylist)

  })

  

  # Grabbing only the 1st data frame:

  output$mydf <- renderTable({

    if(input$goButton==0) return(NULL)

    myout()$dataframe1

  })

  

  observe({

    lapply(1:input$NumRuns, function(i) {

      output[[paste0("downloadData", i)]] <- downloadHandler(

        filename = function() { paste(input$downloadData,i, " ",Sys.Date(),".csv",sep="") },

        content = function(file) {

          write.csv(myout()$dataframe[i],file,row.names=F)

    })

  })

  

})