如何从.csv文件中读取特定列的数据？

Question

I am trying to make a Shiny App which can read a.csv file and display the specific data in the app. For example, if I choose number 3 and type 2, "H" will be displayed in the app.

Below are the sample codes:

library(shiny)
library(shinydashboard)
library(shinyWidgets)

ui = dashboardPage(
     dashboardHeader(title = "Selection"),
     dashboardSidebar(disable = TRUE), 
     dashboardBody(uiOutput("body")))



server = function (input, output, session) {

  output$body <- renderUI({ 
    box(numericInput('number', "Choose a number:", value = NULL, min = 1, max = 5),
        br(),
        selectInput('type', "Choose a type:", choices = list("Type 1", "Type 2")),
        br(),
        textOutput("my_selection"),
        br()

    )})


  selection_table <- reactive({read.csv("selection.csv", header = T, sep = "," , check.names = FALSE, col.names = TRUE)})


  output$my_selection = reactive({
    selection = ifelse(input$number == 1 & input$type == "Type 1", selection_table()$selection_1[1], 
                       ifelse(input$number == 2 & input$type == "Type 1", selection_table()$selection_1[2],
                              ifelse(input$number == 3 & input$type == "Type 1", selection_table()$selection_1[3],
                                     ifelse(input$number == 4 & input$type == "Type 1", selection_table()$selection_1[4],
                                            ifelse(input$number == 5 & input$type == "Type 1", selection_table()$selection_1[5],
                                                   ifelse(input$number == 1 & input$type == "Type 2", selection_table()$selection_2[1], 
                                                          ifelse(input$number == 2 & input$type == "Type 2", selection_table()$selection_2[2],
                                                                 ifelse(input$number == 3 & input$type == "Type 2", selection_table()$selection_2[3],
                                                                        ifelse(input$number == 4 & input$type == "Type 2", selection_table()$selection_2[4],
                                                                               ifelse(input$number == 5 & input$type == "Type 2", selection_table()$selection_2[5]))))))))))




    selection
  })

}
shinyApp(ui,server)

And this is the sample data in the.csv file:

age selection_1   selection_2
1    A             F
2    B             G
3    C             H
4    D             I
5    E             J

Appreciate any help!! Thanks!

Answer 1

If the data in the csv isn't being changed dynamically when the app is running then I would move the read.csv to the header so that it is loaded once into memory when the application is launched.

library(shiny)
library(shinydashboard)
library(shinyWidgets)

ui = dashboardPage(
     dashboardHeader(title = "Selection"),
     dashboardSidebar(disable = TRUE), 
     dashboardBody(uiOutput("body")))

df <- read.csv("selection.csv", header = T, sep = "," , check.names = FALSE, col.names = TRUE)

server = function (input, output, session) { #### ...rest of your app code

Your nested ifelse code is complicated - it would probably be easier to try and rename the data in the csv to make it easier to sub-set, eg

output <- df[input1, input2] 

...and pass the output of that subsetting operation to the UI.