07. 在shiny 中使用脚本和包

参见：https://shiny.rstudio.com/tutorial/written-tutorial/lesson5/

shiny 执行的顺序是，首先当适应shinyapp 允许命令后，会在全局环境中加载相关的内容。

而只有server 中的render 函数，才会在使用用户第一访问shiny 或通过交互按钮切换显示内容时才会被反复执行。

在运行官方提供的代码前，先解决一下先前的无法通过获得交互选项结果修改输出表格的问题。

非常的神奇，无论如何尝试，只有在使用swich 根据结果的判断来进行返回值的情况下，才能够正确的进行显示：

# Define server logic ----
server <- function(input, output) {
  output$test_df <- renderDataTable({ 
    data <- switch(input$select,
                   "Herb info" = test_list$`Herb info`,
                   "ingredient info" = test_list$`ingredient info`)
    # a <- input$select
    # data <- test_list$a
    # data <- test_list$`input$select`
    #data
  })
  output$test_txt <- renderText({
    paste0("output is ", input$select)
  })
}

看来以后绑定switch 了。

可是，如果是批量的进行赋值或者是连续性内容进行判断赋值呢？switch 有没有替代品呢？

我们还可以玩的更高级，将参数以列表的形式传递给函数：

server <- function(input, output) {
  output$map <- renderPlot({
    args <- switch(input$var,
      "Percent White" = list(counties$white, "darkgreen", "% White"),
      "Percent Black" = list(counties$black, "black", "% Black"),
      "Percent Hispanic" = list(counties$hispanic, "darkorange", "% Hispanic"),
      "Percent Asian" = list(counties$asian, "darkviolet", "% Asian"))
    args$min <- input$range[1]
    args$max <- input$range[2]
    do.call(percent_map, args)
  })
}

全部内容如下：

##################################################
## Project: Rescue the Princess
## File name: app.R
## Date: Fri Jun 25 16:47:13 2021
## Author: Peng
## R_Version: R version 4.0.2 (2020-06-22)
## R_Studio_Version: 1.4.1106
## Platform Version: Windows 10 x64 (build 19042)
##################################################
# # pre-loaded data&library -----------------------------------------------
# Load packages ----
library(shiny)
library(maps)
library(mapproj)
# Load data ----
counties <- readRDS("./app-census/data/counties.rds")
# Source helper functions -----
source("helpers.R")
# User interface ----
ui <- fluidPage(
  titlePanel("censusVis"),
  sidebarLayout(
    sidebarPanel(
      helpText("Create demographic maps with 
        information from the 2010 US Census."),
      selectInput("var", 
                  label = "Choose a variable to display",
                  choices = c("Percent White", "Percent Black",
                              "Percent Hispanic", "Percent Asian"),
                  selected = "Percent White"),
      sliderInput("range", 
                  label = "Range of interest:",
                  min = 0, max = 100, value = c(0, 100))
    ),
    mainPanel(plotOutput("map"))
  )
)
# Server logic ----
server <- function(input, output) {
  output$map <- renderPlot({
    data <- switch(input$var, 
                   "Percent White" = counties$white,
                   "Percent Black" = counties$black,
                   "Percent Hispanic" = counties$hispanic,
                   "Percent Asian" = counties$asian)
    color <- switch(input$var, 
                    "Percent White" = "darkgreen",
                    "Percent Black" = '#fdcc8a',
                    "Percent Hispanic" = '#fc8d59',
                    "Percent Asian" = '#d7301f')
    legend.title <- switch(input$var, 
                           "Percent White" = "% White",
                           "Percent Black" = '% Black',
                           "Percent Hispanic" = '% Hispanic',
                           "Percent Asian" = '% Asian')
    percent_map(var = data, color = color, legend.title = legend.title, input$range[1], input$range[2])
  })
}
# Run app ----
shinyApp(ui, server)