Question

可以将以下代码复制并粘贴到RStudio中并运行：

salary <- c(45434,54834, 685485)
name <- c("john smith", "willy mcghee", "john paul stevens")
df <- data.frame(salary, name)
library(shiny)
library(dplyr)
# Define UI for application that draws a histogram
ui <- fluidPage(
    # Title 
  titlePanel("title"),
     # this is the sidebar on the left when you run 
  sidebarLayout(
    sidebarPanel(
        # selection of names
    selectInput("people",
            label = "select the investor",
            choices = c("john smith", "willy mcghee", "john paul stevens"))
       ),
   mainPanel(
      helpText("main panel text"),
      textOutput("textsummary")
   )
 )
)
# Define server logic required to draw a histogram
server <- function(input, output) {
   vals <- reactiveValues()
 observe({
   vals$people <- input$people
   vals$famousNetWorth <- df %>% filter(name == input$people)
} )

 output$textsummary <- renderText({
   paste(" the salary for ",vals$people, " is ",   vals$famousNetWorth)
    })
  }
# Run the application 
shinyApp(ui = ui, server = server)

这是我得到的输出：

问题为什么输出打印两次（以黄色突出显示）？问题肯定源于尝试从我的salary中的df列中选择值以匹配用户选择的名称＆＃39;除了我努力寻找更好的名称反应方式选择与name输入匹配的工资。下一张图片是硬编码的 - 这就是我想要的样子：

Answer 1

这发生了（正如评论中提到的@greg L）filter步的输出仍然是data.frame，其中有两列，如原始'df'。

df %>% 
    filter(name == "john smith")
#  salary       name
#1  45434 john smith

使用paste，它会遍历每一列，并paste带有列值的'salary：'字符串

paste("salary:", df %>% 
                  filter(name == "john smith"))  
#[1] "salary: 45434" "salary: 2"

如果我们看第二个案例，看起来很困惑，但请查看'df'的str

str(df)
#'data.frame':  3 obs. of  2 variables:
# $ salary: num  45434 54834 685485
#  $ name  : Factor w/ 3 levels "john paul stevens",..: 2 3 1

由于'name'为factor类，因此存储模型为integer

df$name
#[1] john smith        willy mcghee      john paul stevens
# Levels: john paul stevens john smith willy mcghee

或查看levels

levels(df$name)
#[1] "john paul stevens" "john smith"        "willy mcghee"

“约翰史密斯”是第二级

df %>% 
  filter(name == "john smith") %>% 
  pull(name) %>% 
  as.integer
#[1] 2

paste factor被强制转换为整数存储模式

我们需要pull“薪水”栏中的vector，即

vals$famousNetWorth <- df %>% 
               filter(name == input$people) %>%
               pull(salary)

-full code

salary <- c(45434,54834, 685485)
name <- c("john smith", "willy mcghee", "john paul stevens")
df <- data.frame(salary, name)
library(shiny)
library(dplyr)
# Define UI for application that draws a histogram
ui <- fluidPage(
  # Title 
  titlePanel("title"),
  # this is the sidebar on the left when you run 
  sidebarLayout(
    sidebarPanel(
      # selection of names
      selectInput("people",
                  label = "select the investor",
                  choices = c("john smith", "willy mcghee", "john paul stevens"))
    ),
    mainPanel(
      helpText("main panel text"),
      textOutput("textsummary")
    )
  )
)
# Define server logic required to draw a histogram
server <- function(input, output) {
  vals <- reactiveValues()
  observe({
    vals$people <- input$people
    vals$famousNetWorth <- df %>% 
                   filter(name == input$people) %>%
                   pull(salary)
  } )

  output$textsummary <- renderText({
    paste(" the salary for ",vals$people, " is ",   vals$famousNetWorth)
  })
}
# Run the application 
shinyApp(ui = ui, server = server)

-output

Console output

Shiny renderText的重复输出

1 个答案: