错误：`data` 必须是一个数据框，或其他可通过`fortify()` 强制的对象，而不是具有类 reactiveExpr/reactive 的 S3 对象

Question

我正在尝试构建一个 Corona 仪表板。如果有人从下拉列表中选择州，则将在图表中显示地区案例。例如。如果有人选择古吉拉特邦，它会在条形图中显示地区案例。有人将其更改为马哈拉施特拉邦，它应该随着马哈拉施特拉邦的地区而更新。 但我得到 “ERROR:data must be a data frame, or other object coercible by fortify(), not an S3 object with class reactiveExpr/reactive”错误。

library(shiny)
library(readxl)
library(ggplot2)
library(dplyr)

ui <- fluidPage(

    # Application title
    titlePanel("Corona Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            selectInput(inputId = "state", 
                        label = "Select the State",
                        choices = unique(data$`Detected State`))
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("stateplot")
        )
    )
)


data <- read_excel("Live Data Worldometer.xlsx", sheet = "IndiaData")
data <- data[,c(-2,-1)]

server <- function(session, input, output) {

    d1 <- reactive({data %>% group_by(`Detected State`) %>% count(`Detected District`) %>% filter(`Detected State` == input$state)
        })

    output$stateplot <- renderPlot({
        ggplot(d1, aes(d1$`Detected District`, d1$n))+geom_bar(stat = "identity")
    })

}

# Run the application 
shinyApp(ui = ui, server = server)

This is the output I am getting

Answer 1

d1 不是数据框，而是需要评估的表达式（reactive 不返回数据框）。在ggplot2中使用前需要激活反应元素

server <- function(session, input, output) {

    d1 <- reactive({
        data %>% group_by(`Detected State`) %>% 
                 count(`Detected District`) %>%
                 filter(`Detected State` == input$state)
        })

    output$stateplot <- renderPlot({
        ggplot(d1(), aes(x = `Detected District`, y = n)) +
             geom_bar(stat = "identity")
    })

}