I'm writing an online table by Shiny of R language, but something confusing stops me.

What I need is:

1. Show the full table for the first time.
2. If you type a number in the input block and submit, just show the top n rows of the table automatically.

What I see is:

DFflt, the variable behind the table, is already changed after submission, but the table on the webpage cannot be reloaded before you refresh the page manually.

What can I do to solve this problem? Thanks!

library(shiny)
library(tidyverse)

DF <- mpg
DFflt <- mpg

ui <- fluidPage(
  numericInput("nrow", "Slice the top n rows of DF", value = 0),
  actionButton("submit", "Submit"),
  actionButton("p_DFflt", "print DFflt in console"),
  div('render DFflt：'),
  tableOutput("table")
  )
server <- function(input, output, session) {

  observeEvent(input$submit, {
    nrow <- input$nrow
    if (nrow > 10) {
      showNotification(str_c("Invalid", type="error")) }
    else { DFflt <<- DF %>% head(nrow) }
  })
  
  observeEvent(input$p_DFflt, { print(DFflt)} )
  
  output$table <- renderTable({DFflt})
}

shinyApp(ui, server)

CodePudding user response：

This should work as you expected:

library(shiny)
library(tidyverse)

DF <- mpg

ui <- fluidPage(
  numericInput("nrow", "Slice the top n rows of DF", value = 0),
  actionButton("submit", "Submit"),
  actionButton("p_DFflt", "print DFflt in console"),
  div('render DFflt：'),
  tableOutput("table")
)
server <- function(input, output, session) {
  
  n_row <- eventReactive(input$submit, {
    input$nrow
  })

  observe({
    if (n_row() > 10) {
    showNotification(str_c("Invalid ", type="error")) 
    }
  })

  output$table <- renderTable({
    if(input$submit == 0){ #  when the submit button is not clicked
      DF
    }else{
      if (n_row() >= 0 & n_row() <= 10) {
        DF %>% head(n_row())
      }
    }
  })
 
 observeEvent(input$p_DFflt, { print(DF)} )
}

shinyApp(ui, server)