R/Shiny - 如何响应式地编写包含 actionButton 的 .csv？

Question

我试图弄清楚如何根据最终用户的选择编写 .csv。所做的选择将子集“geodata.csv”并在应用程序文件夹中写入单独的“solution.csv”文件。

注意 - 我创建了一个 github repo使解决问题更容易。它包含 geodata.csv、ui.R 和 server.R 但还没有 solution.csv!

geodata.csv

Postcode,HC,BSL,Position Location
10,1,A,C
10,1,A,D
10,1,A,D
11,1,B,C
11,1,B,C

ui.R

shinyUI(
 pageWithSidebar(
  headerPanel('Min. working example - write a csv based on user input'),

  sidebarPanel(
   selectInput("filter1", "First selection:" 
              , choices = c(Choose='', "A", "B")
              #, multiple=T
              ),

   selectInput("filter2", "Second selection:", 
              choices = c(Choose='', "C", "D")
              ),
   br(),
   p("Include actionButton to prevent write occuring before user finalises selection"),  
   actionButton("generateButton","Write Data")    
  ),
  mainPanel()
 )
)

server.R

# Load data
setwd("/Users/lukesingham/SOtestApp")
geodata <- read.csv("geodata.csv", na.string = "#N/A", row.names=NULL)

# Reactivity to subset data ####
shinyServer(function(input, output) {
  geodatasetInput <- reactive({

    # BSL switch
    selection <-switch(input$BSL
                       , A = "A"
                       , B = "B"
                       ) 
    # Location switch    
    selection2 <-switch(input$Location
                       , C = "C"
                       , D = "D"
                       )

    # subset based on selection
    Subgeodata <- subset(geodata, BSL == selection & Position.Location == selection2)

    # Execute selections on data upon button-press
    input$generateButton

    # aggregate by postcode
    Subgeodata <- Subgeodata[1:2] #no longer need other columns
    AggSubGdata <- aggregate(. ~ Postcode, data=Subgeodata, FUN=sum)
    isolate(write.csv(AggSubGdata
              , file = "/Users/lukesingham/SOtestApp/solution.csv"
              , row.names=F
    ))
  })
})

solution.csv

例如，根据用户对 A 和 D 的选择，解决方案文件应如下所示:

Postcode,HC
10,2

Answer 1

下面是工作示例:

# Load data
setwd("/Users/lukesingham/SOtestApp")
geodata <- read.csv("geodata.csv", na.string = "#N/A", row.names=NULL)

# Reactivity to subset data ####
shinyServer(function(input, output) {
  geodatasetInput <- observe({

    # Execute selections on data upon button-press
    if(input$generateButton == 0) return()

    inp.BSL <- isolate(input$filter1)
    inp.loc <- isolate(input$filter2)
    if (inp.BSL=='' | inp.loc=='') return()

    # BSL switch
    selection <-switch(inp.BSL
                       , A = "A"
                       , B = "B"
                       ) 
    # Location switch    
    selection2 <-switch(inp.loc
                       , C = "C"
                       , D = "D"
                       )

    # subset based on selection
    Subgeodata <- subset(geodata, BSL == selection & Position.Location == selection2)

    # browser()
    # aggregate by postcode
    Subgeodata <- Subgeodata[1:2] #no longer need other columns
    AggSubGdata <- aggregate(. ~ Postcode, data=Subgeodata, FUN=sum)
    write.csv(AggSubGdata
              , file = "solution.csv"
              , row.names=F
    )
  })
})

以及对您的代码的简短分析:

1. geodatasetInput 根本没有启动的主要原因是因为它是一个reactive() 表达式。 reactive() 仅在 @pops 的答案中被 renderTable() 之类的其他东西调用时才被评估。如果想让它自己执行，应该是observe()。

2. 在 observe() 表达式的开头使用 input$generateButton 可能是个好主意。

3. 在ui.R中，你调用了一个数字输入域filter1，但是你试图以input$BSL的形式获取它的值> 来自 server.R; filter2 也是如此。

4. 您希望 geodataSetInput 仅在 generateButton、所有其他 input$ 和带有 geodataSetInput 的响应式(Reactive)表达式上触发 应该与 isolate() 隔离。另一方面，没有必要隔离 write.csv，因为这个特定的函数调用不涉及任何“动态”参数。