基于动态更新的selectInput动态更新selectInput

Question

我试图根据动态更新的selectInput()值动态更新selectInput()值。我可以获得动态更新的第一个值，但是当我尝试使用这些值来更新进一步的值时，我会得到一个错误：

Warning: Error in [.data.frame: undefined columns selected
  [No stack trace available]

我要找的行为是：

从dataframe

• Filter中选择变量，从variable

• Select中选择值，从dataframe

• Filter中选择另一个变量，从变量

中选择值

一旦一个变量被选中，我不希望这个选择在以后的选择中作为选项出现。我希望筛选器选项基于所选变量填充。

下面是一个可重复的例子：

library('shiny')

#create sample data
df = data.frame('first.name' = c('peter', 'paul', 'patricia'), 
                  'family.name' = c('smith', 'jones', 'gibbon'), 
                  'language' = c('english', 'french', 'spanish'))
#create the UI
ui <- fluidPage(
  
  #Create first selector for variable 1, based on column names
  selectInput(inputId = 'var1', 
              label = 'Variable 1', 
              choices = colnames(df)),
  
  #create selector for filtering, populated based on the selection for variable 1
  #leave values for label and choice blank - to be populated by updateSelectInput()
  selectInput(inputId = 'var1_subselect', 
              label = '', 
              choices = ''),
  
  #create selector for variable 2, should not include variable one
  selectInput(inputId = 'var2', 
              label = 'Variable 2', 
              choices = ''),
  
  #create selector for filtering, populated based on the selection for variable 2
  selectInput(inputId = 'var2_subselect', 
              label = '', 
              choices = '')
  
)

#Create the server
server <- function(session, input, output) {
 observe({
   updateSelectInput(session, 
                     inputId = 'var1_subselect', #for var1_subselect
                     label = paste(input$var1, 'selection:'), #Get the label from the value for var1
                     choices = unique(df[input$var1])) #Get the choices based on unique values far var1
 })
  
  observe({
    updateSelectInput(session, 
                      inputId = 'var2', #for var2
                      label = 'Variable 2', #Label is standard 
                      choices = setdiff(colnames(df), input$var1)) #Get choices from the colnames for the df, excluding the choice for var1
  })
  
  #Everything works up to this point, however when i add the following effort to filter the values for var 2, i get an error
  
  observe({
    updateSelectInput(session, 
                      inputId = 'var2_subselect', #for var2_subselect
                      label = paste(input$var2, 'selection:'), #Get the label from the value for var2
                      choices = unique(df[input$var2])) #Get the choices based on the unique values of var2
  })
  
}

#call the app
shinyApp(ui, server)

当我调用第三个observe({})函数时，就会得到一个错误。我猜想这是因为我试图调用一个基于反应性输入的输入。

我试图使用UI中的uiOutput()和服务器中的renderUI({})来解决这个问题，但是当我尝试基于动态更新的内容动态更新内容时，我遇到了同样的问题。

Answer 1

一个小而简单的解决方法是使用[[而不是[过滤数据。在本文中，The difference between bracket [ ] and double bracket [[ ]] for accessing the elements of a list or dataframe解释了两者之间的较高层次差异。

在这里，[[总是返回一个向量，而[返回一个数据文件，它在大多数情况下都能正常工作，但是在没有为var2做选择时失败，这意味着var2是空的。

[返回

df['']

[

(df，"")中的.data.frame错误:选定的未定义列

这是您收到的错误消息。

而对于[[，它返回NULL。

df[['']]
#NULL

这是choices参数在selectInput中所接受的。

完整的代码-

library(shiny)

#create sample data
df = data.frame('first.name' = c('peter', 'paul', 'patricia'), 
                'family.name' = c('smith', 'jones', 'gibbon'), 
                'language' = c('english', 'french', 'spanish'))
#create the UI
ui <- fluidPage(
  
  #Create first selector for variable 1, based on column names
  selectInput(inputId = 'var1', 
              label = 'Variable 1', 
              choices = colnames(df)),
  
  #create selector for filtering, populated based on the selection for variable 1
  #leave values for label and choice blank - to be populated by updateSelectInput()
  selectInput(inputId = 'var1_subselect', 
              label = '', 
              choices = ''),
  
  #create selector for variable 2, should not include variable one
  selectInput(inputId = 'var2', 
              label = 'Variable 2', 
              choices = ''),
  
  #create selector for filtering, populated based on the selection for variable 2
  selectInput(inputId = 'var2_subselect', 
              label = '', 
              choices = '')
  
)

#Create the server
server <- function(session, input, output) {
  observe({
    updateSelectInput(session, 
                      inputId = 'var1_subselect', #for var1_subselect
                      label = paste(input$var1, 'selection:'), #Get the label from the value for var1
                      choices = unique(df[[input$var1]])) #Get the choices based on unique values far var1
  })
  
  observe({
    updateSelectInput(session, 
                      inputId = 'var2', #for var2
                      label = 'Variable 2', #Label is standard 
                      choices = setdiff(colnames(df), input$var1)) #Get choices from the colnames for the df, excluding the choice for var1
  })
  
  observe({
     updateSelectInput(session, 
                       inputId = 'var2_subselect', #for var2_subselect
                       label = paste(input$var2, 'selection:'), #Get the label from the value for var2
                       choices = unique(df[[input$var2]])) #Get the choices based on the unique values of var2
   })
  
}

#call the app
shinyApp(ui, server)

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