1

I'm developping an R Shiny-based application. I want to keep my input consistent with available data, thus I update the selected values in selectInput. When I change selected value in input 1, then the value of input 2 is updated, then the data is updated (just once). OK BUT if I change selected value in input 2, then the data is updated, then the value of input 1 is updated, then the data is updated AGAIN. Check out the "check latest_value" that is printed twice.

Initially I used renderUI rather than updateSelectInput, but at initialisation, the data is computed twice. 

library(shiny)
library(DT)
library(dplyr)
my_data=data.frame(CO2)
# Running a Shiny app object
app <- shinyApp(
  ui = bootstrapPage(
    selectInput('type','Choix du type',choices = unique(my_data$Type)),
    uiOutput('plant_ui'),
    DTOutput('plot')
  ),
  server = function(input, output) {

    data=reactive({
      # req(input$type)
      my_data_temp=my_data
      if(length(input$type)>0){
        my_data_temp=my_data_temp%>%filter(Type%in%input$type)
      }
      if(length(input$plant)>0){
        my_data_temp=my_data_temp%>%filter(Plant%in%input$plant)
      }

      my_data_temp
    })

    latest_plant_value=reactive({
      if(is.null(input$plant))data()$Plant[1]
      else input$plant
    })


    output$plant_ui=renderUI({
      sub_data=data()
      selectInput(inputId = 'plant',"filtre par plant",choices = unique(sub_data$Plant),
                  selected=latest_plant_value())
    })

    output$plot <- renderDT({ 
      print("check latest_value")
      datatable(data()) })
  }
)
runApp(app)

That's why I decided to use updateSelectInput based on this Alternate control of a sliderInput between a derived value and user selected value but the sequential structure of the code makes the data to be computed twice when I change input 2 value.

library(shiny)
library(DT)
library(dplyr)
my_data=data.frame(CO2)
# Running a Shiny app object
app <- shinyApp(
  ui = bootstrapPage(
    selectInput('type','Choix du type',choices = unique(my_data$Type),selected=my_data$Type[1]),
    selectInput('plant','Choix du type',choices = unique(my_data$Plant),selected=my_data$Plant[1]),
    DTOutput('plot')
  ),
  server = function(input, output,session) {

    data=reactive({
      # req(input$type)
      my_data_temp=my_data
      if(length(input$type)>0){
        my_data_temp=my_data_temp%>%filter(Type%in%input$type)
      }
      if(length(input$plant)>0){
        my_data_temp=my_data_temp%>%filter(Plant%in%input$plant)
      }

      my_data_temp
    })

    observeEvent(input$type,{
      print("update type changed")
      updateSelectInput(session, "plant",
                        selected =  unique(my_data%>%filter(Type%in%input$type)%>%.$Plant)[1])
    })
    observeEvent(input$plant,{
      print("update plant changed")
      updateSelectInput(session, "type",
                        selected =  unique(my_data%>%filter(Plant%in%input$plant)%>%.$Type)[1])
    })

   output$plot <- renderDT({ 
     print("check latest_value")

     datatable(data()) })
  }
)
runApp(app)

Fixes like this one don't work in that case because I'm not trying to achieve the same thing three interdependent selectInput in R/Shiny application

I want the default selected value of each input to be consistent so that the filter returns at least 1 value. This of any input I change.

4

2 回答 2

2

解决此问题的一种方法是创建一个reactiveVal告诉应用程序正在进行更新操作，并要求data等到该标志返回 False 后再运行。

我在您的第二个闪亮应用程序中添加了 5 行：

至server()：

# Create update in progress flag
updating_type_inprogress <- reactiveVal(FALSE)

至observeEvent(input$type ...：

# When type is changed, set flag to TRUE
updating_type_inprogress(TRUE)

至observeEvent(input$plant ...：

# Once this function has run, the updating operation is done
updating_type_inprogress(FALSE)

至data()：

# Stops updating data() if the in-progress flag is TRUE
req(!updating_type_inprogress())

至renderDT()：

# Stops updating renderDT() if the in-progress flag is TRUE
#  this is probably optional unless there's resource-intensive code
#    that doesn't depend on changes in data()
req(!updating_type_inprogress())

这是整个代码：

library(shiny)
library(DT)
library(dplyr)
my_data=data.frame(CO2)
# Running a Shiny app object
app <- shinyApp(
    ui = bootstrapPage(
        selectInput('type','Choix du type',choices = unique(my_data$Type),selected=my_data$Type[1]),
        selectInput('plant','Choix du type',choices = unique(my_data$Plant),selected=my_data$Plant[1]),
        DTOutput('plot')
    ),
    server = function(input, output,session) {

        data=reactive({
            req(!updating_type_inprogress())
            print(input$type)
            print(input$plant)
            my_data_temp=my_data
            if(length(input$type)>0){
                my_data_temp=my_data_temp%>%filter(Type%in%input$type)
            }
            if(length(input$plant)>0){
                my_data_temp=my_data_temp%>%filter(Plant%in%input$plant)
            }

            my_data_temp
        })

        observeEvent(input$type,{
            updating_type_inprogress(TRUE)
            updateSelectInput(session, "plant",
                              selected =  unique(my_data%>%filter(Type%in%input$type)%>%.$Plant)[1])
        })
        observeEvent(input$plant,{
            updating_type_inprogress(FALSE)
            updateSelectInput(session, "type",
                              selected =  unique(my_data%>%filter(Plant%in%input$plant)%>%.$Type)[1])
        })

        updating_type_inprogress <- reactiveVal(FALSE)

        output$plot <- renderDT({ 
            req(!updating_type_inprogress())
            print("check latest_value")
            datatable(data()) })
    }
)
runApp(app)

如您所见，当您更改 时input$type，data()andrenderDT()函数只运行一次，并使用正确更新的值：

[1] "check latest_value"
[1] "Quebec"
[1] "Qn1"
[1] "check latest_value"
[1] "Mississippi"
[1] "Mn1"
[1] "check latest_value"
[1] "Quebec"
[1] "Qn1"
于 2019-04-12T18:12:45.057 回答
1

有趣的问题，不容易解决！有趣的是，你所要求的并不是你所需要的。观察：

  1. 如果用户在 Input1 为“Mississippi”时选择Qn2 ，您首先在Quebec上设置 Input1 ，然后在Qn1上硬设置Input2 ，从而改变用户的选择。这是不好的。
  2. 一旦两个输入中的任何一个发生更改，数据表就会始终更新，因此需要对表进行多次重新计算。

因此，解决方案是双重的：

  1. 不要覆盖用户的选择，例如Qc2到Qc1。我为此使用了if条件。
  2. 安装watchguard以仅在其内容实际更改时更新数据表。我使用reactiveVal()来执行此操作，仅当两个输入的选择有效时（即结果集大于 0 时）才更新。

请参阅下面的结果。观察控制台输出以观察决定。

library(shiny)
library(DT)
library(dplyr)
my_data=data.frame(CO2)

shinyApp(
  ui = bootstrapPage(
    selectInput('type','Choix du type',choices = unique(my_data$Type),selected=my_data$Type[1]),
    selectInput('plant','Choix du plant',choices = unique(my_data$Plant),selected=my_data$Plant[1]),
    DTOutput('plot')
  ),
  server = function(input, output,session) {

    latest_data <- reactiveVal(my_data)
    observe({
      result <- my_data %>% filter(Type %in% input$type, Plant %in% input$plant)

      if(nrow(result) > 0){
        latest_data(result)
      }else{
        cat(format(Sys.time(), "%H:%M:%S"), "Didn't update the dataframe because the choice was not valid.\n")
      }
    })

    observeEvent(input$type,{
      if(! input$plant %in% my_data$Plant[my_data$Type == input$type]){
        old <- input$plant
        new <- my_data %>% filter(Type %in% input$type) %>% slice(1) %>% pull(Plant) %>% as.character()
        updateSelectInput(session, "plant", selected = new)
        cat(format(Sys.time(), "%H:%M:%S"), "Updated input$plant from", old, "to", new, "so that it represents a valid choice for", input$type, "\n")
      }else{
        cat(format(Sys.time(), "%H:%M:%S"), "Didn't update input$plant", input$plant, "because it is a valid choice for", input$type, "already\n")
      }
    })
    observeEvent(input$plant,{
        updateSelectInput(session, "type",
                          selected = my_data %>% filter(Plant %in% input$plant) %>% slice(1) %>% pull(Type))
    })

    output$plot <- renderDT({ 
      cat(format(Sys.time(), "%H:%M:%S"), "updating datatable to only include", isolate(input$plant), "and", isolate(input$type), "\n\n")
      latest_data()
      datatable(latest_data())
    })
  }
)

解决方案的gif

于 2019-04-12T18:16:54.537 回答