How to activate undo button for previous 4 actions in R Shiny

Question

I am creating a R shiny app with buttons like browse, SpitColumn, deleting rows, values, and columns. Everything functions as it should. I have included a "undo" button, but I'm not sure how to make it work in the server function, also how to undo the previous four actions.

Could someone please assist me?

csv data

ID  Type   Range
21  A1 B1   100
22  C1 D1   200
23  E1 F1   300

app.R

library(shiny)
library(reshape2)
library(DT)
library(tibble)


###function for deleting the rows
splitColumn <- function(data, column_name) {
  newColNames <- c("Unmerged_type1", "Unmerged_type2")
  newCols <- colsplit(data[[column_name]], " ", newColNames)
  after_merge <- cbind(data, newCols)
  after_merge[[column_name]] <- NULL
  after_merge
}
###_______________________________________________
### function for inserting a new column

fillvalues <- function(data, values, columName){
  df_fill <- data
  vec <- strsplit(values, ",")[[1]]
  df_fill <- tibble::add_column(df_fill, newcolumn = vec, .after = columName)
  df_fill
}

##function for removing the colum

removecolumn <- function(df, nameofthecolumn){
  df[ , -which(names(df) %in% nameofthecolumn)]
}

### use a_splitme.csv for testing this program

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      fileInput("file1", "Choose CSV File", accept = ".csv"),
      checkboxInput("header", "Header", TRUE),
      actionButton("Splitcolumn", "SplitColumn"),
      uiOutput("selectUI"),
      actionButton("deleteRows", "Delete Rows"),
      textInput("textbox", label="Input the value to replace:"),
      actionButton("replacevalues", label = 'Replace values'),
      actionButton("removecolumn", "Remove Column"),
      actionButton("Undo", 'Undo')
    ),
    mainPanel(
      DTOutput("table1")
    )
  )
)

server <- function(session, input, output) {
  rv <- reactiveValues(data = NULL)
  
  observeEvent(input$file1, {
    file <- input$file1
    ext <- tools::file_ext(file$datapath)
    
    req(file)
    
    validate(need(ext == "csv", "Please upload a csv file"))
    
    rv$data <- read.csv(file$datapath, header = input$header)
    
  })
  
  output$selectUI<-renderUI({
    req(rv$data)
    selectInput(inputId='selectcolumn', label='select column', choices = names(rv$data))
  })
  
  
  observeEvent(input$Splitcolumn, {
    rv$data <- splitColumn(rv$data, input$selectcolumn)
  })
  
  observeEvent(input$deleteRows,{
    if (!is.null(input$table1_rows_selected)) {
      rv$data <- rv$data[-as.numeric(input$table1_rows_selected),]
    }
  })
  
  output$table1 <- renderDT({
    rv$data
  })
  observeEvent(input$replacevalues, {
    rv$data <- fillvalues(rv$data, input$textbox, input$selectcolumn)
  })
  observeEvent(input$removecolumn, {
    rv$data <- removecolumn(rv$data,input$selectcolumn)
  })
}

shinyApp(ui, server)

score 1 · Accepted Answer · answered Aug 23 '21 at 12:34

Just keep the original file you read in as a separate reactiveValues object and assign it to rv$data when the Undo button is pressed. Try this

server <- function(session, input, output) {
  rv <- reactiveValues(data = NULL, orig=NULL)
  
  observeEvent(input$file1, {
    file <- input$file1
    ext <- tools::file_ext(file$datapath)
    
    req(file)
    
    validate(need(ext == "csv", "Please upload a csv file"))
    
    rv$orig <- read.csv(file$datapath, header = input$header)
    rv$data <- rv$orig
  })
  
  output$selectUI<-renderUI({
    req(rv$data)
    selectInput(inputId='selectcolumn', label='select column', choices = names(rv$data))
  })
  
  
  observeEvent(input$Splitcolumn, {
    rv$data <- splitColumn(rv$data, input$selectcolumn)
  })
  
  observeEvent(input$deleteRows,{
    if (!is.null(input$table1_rows_selected)) {
      rv$data <- rv$data[-as.numeric(input$table1_rows_selected),]
    }
  })
  
  output$table1 <- renderDT({
    rv$data
  })
  observeEvent(input$replacevalues, {
    rv$data <- fillvalues(rv$data, input$textbox, input$selectcolumn)
  })
  observeEvent(input$removecolumn, {
    rv$data <- removecolumn(rv$data,input$selectcolumn)
  })
  observeEvent(input$Undo, {
    rv$data <- rv$orig
  })
}

Please accept my apologies; my previous comments were incorrect; yes, it works just nicely. However, I want the operation to be completed anytime I press the 'Undo' button, such as Ctrl+Z. My expectation is that when I click only once, it should not perform all of the preceding processes. — Kevin Tracey, Aug 23 '21 at 13:39
Perhaps you should post this as a new question. I am not sure I fully understand your needs. I think I have answered your original question. — YBS, Aug 23 '21 at 13:52

How to activate undo button for previous 4 actions in R Shiny

1 Answers1