Question

我正在尝试在Shiny的动态sql查询中使用selectInput但反应状态似乎出错了：

没有活动的反应上下文时，不允许操作。（你试图做一些只能在反应式表达式或观察者内部完成的事情。）

我实际上正在使用带有sql查询的RODBC，但这是尝试重现的例子。

服务器：

data(citytemp, package = "highcharter")

function(input, output) {
  getCityData <- function(selectedCity) {
    return(citytemp[[selectedCity]])

    # hardcoded : 
    # return(citytemp$tokyo)

    # dynamic sql query
    # sql <- paste0("select * from cities where name = ", selectedCity)
  }

  cityData <- getCityData(input$cityFilter)

  #render highchart with cityData

}

用户界面：

library("shiny")
library("shinydashboard")

selectInput("cityFilter", label = "City", choices = list("Tokyo" = "tokyo", "London" = "london", "Berlin" = "berlin"))
box(width = 6, highchartOutput("highchart"))

Answer 1

由于您使用的是客户输入，因此必须使用reactive表达式或observer，请尝试以下操作：

  cityData <- reactive({getCityData(input$cityFilter)})
  output$highchart <- renderHighchart({cityData()})

Answer 2

基本示例，请务必说明reactive({getCityData(input$cityFilter)})。

library(shiny)
library(shinydashboard)
library(highcharter)
ui <- dashboardBody(
  selectInput("cityFilter", label = "City", choices = list("Tokyo" = "tokyo", "London" = "london", "Berlin" = "berlin")),
  box(width = 6, highchartOutput("highchart") )
)
server = function(input, output){
  data(citytemp, package = "highcharter")
  getCityData <- function(selectedCity) {
    return(citytemp[[selectedCity]])
    # hardcoded : 
    # return(citytemp$tokyo)
    # dynamic sql query
    # sql <- paste0("select * from cities where name = ", selectedCity)
  }
  cityData <- reactive({getCityData(input$cityFilter)})
  output$highchart <- renderHighchart({
    selectedCityData <- cityData()
    print("selected city data is")
    print(selectedCityData)
    hc <- highchart(type = "chart")  %>%
      hc_add_series( name = input$cityFilter,
                     data = selectedCityData  )
    theme <- hc_theme_null()
    hc <- hc %>% hc_add_theme(theme)
    return(hc)
  })
}
shinyApp(ui=ui, server=server)

Answer 3

如果有人在寻找，那么这就是工作解决方案。

github : dynamic query from reactive shiny widget

在动态查询中使用R Shiny selectInput

3 个答案: