Reading Objects from Shiny Output Object Not Allowed

Reading objects from shiny output object not allowed?

The issue is that the output object is generating all of the web display stuff as well. Instead, you need to pull the data separately for the download. You could do it with a second call to brushedPoints in the download code. Better, however, is to use a reactive() function to do it just once, then call that everywhere that you need it. Here is how I would modify your code to make that work:

data(iris)

ui <- basicPage(
  plotOutput("plot1", brush = "plot_brush"),
  verbatimTextOutput("info"),mainPanel(downloadButton('downloadData', 'Download'))
)

server <- function(input, output) {
  output$plot1 <- renderPlot({
    ggplot(iris,aes(x=Sepal.Width,y=Sepal.Length)) + geom_point(aes(color=factor(Species))) + theme_bw()
  })

  selectedData <- reactive({
    brushedPoints(iris, input$plot_brush)
  })

  output$info <- renderPrint({
    selectedData()
  })

  output$downloadData <- downloadHandler(
    filename = function() { 
      paste('SelectedRows', '.csv', sep='') },
    content = function(file) {
      write.csv(selectedData(), file)
    }
  )

}

shinyApp(ui, server)

(Note, with ggplot2, you do not need to explicitly set xvar and yvar in brushedPoints. So, I removed it here to increase the flexibility of the code.)

I am not aware of any "lasso" style free drawing ability in shiny (though, give it a week -- they are constantly adding fun tools). However, you can mimic the behavior by allowing user to select multiple regions and/or to click on individual points. The server logic gets a lot messier, as you need to store the results in a reactiveValues object to be able to use it repeatedly. I have done something similar to allow me to select points on one plot and highlight/remove them on other plots. That is more complicated than what you need here, but the below should work. You may want to add other buttons/logic (e.g., to "reset" the selections), but I believe that this should work. I did add a display of the selection to the plot to allow you to keep track of what has been selected.

data(iris)

ui <- basicPage(
  plotOutput("plot1", brush = "plot_brush", click = "plot_click")
  , actionButton("toggle", "Toggle Seletion")
  , verbatimTextOutput("info")
  , mainPanel(downloadButton('downloadData', 'Download'))
)

server <- function(input, output) {
  output$plot1 <- renderPlot({

    ggplot(withSelected()
           , aes(x=Sepal.Width
                 , y=Sepal.Length
                 , color=factor(Species)
                 , shape = Selected)) +
      geom_point() +
      scale_shape_manual(
        values = c("FALSE" = 19
                   , "TRUE" = 4)
      , labels = c("No", "Yes")
      , name = "Is Selected?"
      ) +
      theme_bw()
  })

  # Make a reactive value -- you can set these within other functions
  vals <- reactiveValues(
    isClicked = rep(FALSE, nrow(iris))
  )

  # Add a column to the data to ease plotting
  # This is really only necessary if you want to show the selected points on the plot
  withSelected <- reactive({
    data.frame(iris
               , Selected = vals$isClicked)
  })

  # Watch for clicks
  observeEvent(input$plot_click, {

    res <- nearPoints(withSelected()
                      , input$plot_click
                      , allRows = TRUE)

    vals$isClicked <-
      xor(vals$isClicked
          , res$selected_)
  })

  # Watch for toggle button clicks
  observeEvent(input$toggle, {
    res <- brushedPoints(withSelected()
                         , input$plot_brush
                         , allRows = TRUE)

    vals$isClicked <-
      xor(vals$isClicked
          , res$selected_)
  })

  # pull the data selection here
  selectedData <- reactive({
    iris[vals$isClicked, ]
  })

  output$info <- renderPrint({
    selectedData()
  })

  output$downloadData <- downloadHandler(
    filename = function() { 
      paste('SelectedRows', '.csv', sep='') },
    content = function(file) {
      write.csv(selectedData(), file)
    }
  )

}

shinyApp(ui, server)

getting error: Reading objects from shinyoutput object not allowed - multiple linear regression model

Without having some data at hand to reproduce your app its hard to spot the error and makes it more of a guessing game.

So my first guess would be, that you're not handling the reactivity in your app correctly. You're render* functions are calling reactive values, but when no file was uploaded and no Regressor was chosen, there is no data to work with, so it will throw an error. I would suggest checking out the Shiny principles of reactivity and the functions observeEvent, req, validate.

Then you can remove the lines with is.null(*), as the req() function does that for you.

Next thought, what is mpg?
And I think you should change summary(modelq()) to summary(modelq) too, as you just want to print the summary of the object and not call the object.

Calling library(shiny) once is enough. ;)

In the prediction you are also calling df, which is not assigned in that function. I added a reactiveValues object, where you can save other objects in a reactive way. And in your second renderUI we add the data to the reactiveValues object like thisdf$file <- df. And in the prediction function you can call the data like this predict(modelq,df$file).

I also changed the regformula to an eventReactive() which will be executed every time you press the action button.

And lastly, I changed to formula creation to as.formula(paste("mpg",'~',paste(input$independents, collapse= "+"))), as if you only call input$independents, it will only take the first argument.

library(shiny)
library(datasets)
library(caret)
library(curl)

ui <- fluidPage(
  titlePanel("My first predictive model"),
  sidebarLayout(
    sidebarPanel(
      fileInput('file1', 'Choose CSV File',
                accept=c('text/csv', 
                         'text/comma-separated-values,text/plain', 
                         '.csv')),
      tags$hr(),
      verbatimTextOutput("smp"),
      uiOutput("dependent"),
      uiOutput("independents"),
      tags$hr(),
      actionButton("action", "Predict!")
    ),
    mainPanel(
      verbatimTextOutput("summary1")
    )
  )
)

server <- function(input, output, session) {
  filedata <- reactive({
    infile <- input$file1
    read.csv(infile$datapath)
  })
  
  df <- reactiveValues(file = NULL)
  
  output$dependent <- renderUI({
    req(input$file1)
    df <- filedata()
    items=names(df)
    names(items)=items
    selectInput("dependent","Select ONE variable as dependent variable from:",items)
  })
  output$independents <- renderUI({
    req(input$file1)
    df <- filedata()
    
    df$file <- df
    
    checkboxGroupInput('independents','Select the regressors', choices = names(df))
  })
  #regression formula
  regformula <- eventReactive(input$action, {
    as.formula(paste("mpg",'~',paste(input$independents, collapse= "+")))
  })
  #model

  output$summary1 <- renderPrint({
    req(regformula())
    req(input$file1)

    modelq <- lm(regformula(),data=mtcars)

    df <- filedata()

    pred1<-predict(modelq,df); 
    names <- df$X
    
    data.frame(X = as.character(names), Prediction = pred1)
  })
}

shinyApp(ui, server)

R Shiny: Error in $.shinyoutput: Reading from shinyoutput object is not allowed.

Found the solution: I just need to replace output$paste0("data", i) by output[[paste0("data", i)]].

Hope this will help somebody

Reading objects from shinyoutput object are not allowed

You are only missing a '-' at the end of your server.R file. If you look closely at your output$gvis you will notice that you are not assigning output$gvis but actually comparing it to your rendered Gvis object with the < operator (which is why you get the error about reading objects from output). Just change the output$gvis < renderGvis({... to output$gvis <- renderGvis({... and everything should work fine.

Issues about this error: Error in $.shinyoutput: Reading from shinyoutput object is not allowed.

I cannot test it because your code sample is not reproducible. But what the error states is that you are trying to access an UI output variable directly in your server. Of course you can access the generated output in your server, but then it becomes an input, right?

This happens when you are checking if output$nivel is either 1 or 2. You should access the nivel variable with input$nivel in your server.

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