How to return a server object in Ui?

Question

I am creating a appshiny to analyze a statistical model. In it the user places the data set and the model is returned. I would like to implement the removal of non-significant variables, but for that I need the variable names of my file to return to selectInput, is it possible to do this?

 library(shiny)

ui <- fluidPage(

  titlePanel("-"),

  sidebarLayout(

    sidebarPanel(

      fileInput(inputId="arquivo", "Selecione o arquivo",accept = ".csv"),

      selectInput(inputId = "insi", "Selecione as variaveis não significativas", choices = names(k) ,multiple = TRUE )

    ),

    mainPanel(

      tabsetPanel(type = "tab",
                  tabPanel("Dados",tableOutput("dados")),
                  tabPanel("Ajuste", verbatimTextOutput("model"))
      )
    )

  )

)

server <- function(input, output) {

  output$dados <- renderTable({

    if(is.null(input$arquivo))     return(NULL)
    k <- read.csv(input$arquivo$datapath, header = TRUE, stringsAsFactors = FALSE)


    if(input$header==FALSE)
    {
      return(k)
    }
    if (input$header==TRUE)
    {
      return(head(k))
    }

  })

  output$model <- renderPrint({

    if(is.null(input$arquivo))     return(NULL)
    k <- read.csv(input$arquivo$datapath, header = TRUE, stringsAsFactors = FALSE)


    v <- ncol(k)
    y <- k[, 1]
    h <- k[, -1]

    mData <- data.frame(vY = y, mX = h)
    colnames(mData) <- c("vY", paste("VX", 2:v, sep = ""))

    mod <- glm(vY ~ ., data = mData, family = binomial)

    print(summary(mod))


  })

}


shinyApp(ui = ui, server = server)

Answer 1

See my comment above and this first answer is not ideal but should work for your purposes (see below for improved answer):

library(shiny)

ui <- fluidPage(

    titlePanel("-"),

    sidebarLayout(

        sidebarPanel(

            fileInput(inputId="arquivo", "Selecione o arquivo",accept = ".csv"),

            selectInput(inputId = "insi", "Selecione as variaveis não significativas", choices = "" ,multiple = TRUE )

        ),

        mainPanel(

            tabsetPanel(type = "tab",
                        tabPanel("Dados",tableOutput("dados")),
                        tabPanel("Ajuste", verbatimTextOutput("model"))
            )
        )

    )

)

server <- function(input, output, session) {

    output$dados <- renderTable({

        if(is.null(input$arquivo))     return(NULL)
        k <- read.csv(input$arquivo$datapath, header = TRUE, stringsAsFactors = FALSE)

        updateSelectInput(session = session, inputId = "insi", choices = names(k))

        return(k)
        #if(input$header==FALSE)
        #{
        #    return(k)
        #}
        #if (input$header==TRUE)
        #{
        #    return(head(k))
        #}

    })

    output$model <- renderPrint({

        if(is.null(input$arquivo))     return(NULL)
        k <- read.csv(input$arquivo$datapath, header = TRUE, stringsAsFactors = FALSE)



        v <- ncol(k)
        y <- k[, 1]
        h <- k[, -1]

        mData <- data.frame(vY = y, mX = h)
        colnames(mData) <- c("vY", paste("VX", 2:v, sep = ""))

        mod <- glm(vY ~ ., data = mData, family = binomial)

        print(summary(mod))


    })

}


shinyApp(ui = ui, server = server)

Update - improved answer

library(shiny)

ui <- fluidPage(

    titlePanel("-"),

    sidebarLayout(

        sidebarPanel(

            fileInput(inputId="arquivo", "Selecione o arquivo",accept = ".csv"),

            selectInput(inputId = "insi", "Selecione as variaveis não significativas", choices = "" ,multiple = TRUE )

        ),

        mainPanel(

            tabsetPanel(type = "tab",
                        tabPanel("Dados",tableOutput("dados")),
                        tabPanel("Ajuste", verbatimTextOutput("model"))
            )
        )

    )

)

server <- function(input, output, session) {

    k <- reactive({
        if(is.null(input$arquivo))     return(NULL)
        k <- read.csv(input$arquivo$datapath, header = TRUE, stringsAsFactors = FALSE)

        updateSelectInput(session = session, inputId = "insi", choices = names(k))

        return(k)
    })

    output$dados <- renderTable({
        req(k())
    })

    output$model <- renderPrint({
        k <- req(k())

        v <- ncol(k)
        y <- k[, 1]
        h <- k[, -1]

        mData <- data.frame(vY = y, mX = h)
        colnames(mData) <- c("vY", paste("VX", 2:v, sep = ""))

        mod <- glm(vY ~ ., data = mData, family = binomial)

        print(summary(mod))


    })

}


shinyApp(ui = ui, server = server)

The main edits:

• Making choices = "" in the ui and then using updateSelectInput() once names(k) exists.
• Adding session to server.
• Making k a reactive.
• Using req().

Please ask if anything needs further explaining.