How to reset a counter that depends of actionsButtons - Shiny?

Question

I have an app that looks like this

library(shiny)
library(DT)

ui <- fluidPage(
  sidebarPanel(numericInput("c1","Example", NA),
           tags$p(actionButton("update", "Update")),
           tags$p(actionButton("reset", "Clear")),
           tags$p(actionButton("restart", "Restart")),
           textOutput("count"),
           htmlOutput("display")
 ),

  mainPanel(  DT::dataTableOutput("example")
           )
)

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

  # stores the current data frame
  values <- reactiveVal(data.frame(A=1, B=2, C=3))

  # update values table on button click
  observeEvent(input$update,{

    old_values <- values()

    A_new <- input$c1
    B_new <- A_new + 2
    C_new <- A_new + B_new

  new_values <- data.frame(A=A_new, B=B_new, C=C_new)

    # attach the new line to the old data frame here:
    new_df <- rbind(old_values, new_values)

    #store the result in values variable
    values(new_df)

    #reset the numeric input to NA  
    updateNumericInput(session, "c1", "Example", NA)

  })

#Delete last row 
   deleteEntry <- observeEvent(input$reset,{
           values( values()[-nrow(values()),])
   })


        updateCounter <- reactiveValues(i = 0)

    ##This output value must be reset to 0    
       output$count <- renderText({
         paste0("Iteractions: ", updateCounter$i)
       })

       observe({
         input$update
         isolate({
           updateCounter$i <- updateCounter$i + 1
         })
       })

       observe({
         input$reset
         isolate(updateCounter$i <- updateCounter$i - 1)
       })

      #Restart
       defaultvalues <- observeEvent(input$restart, {
         isolate(updateCounter$i == 0)
         values( values()[1,])
         updateCounter <<- reactiveValues(i = 0)
       }) 

    Total <- reactive({ colSums(values()[3]) })

      output$display  <- renderText({
        partialsum <-Total()
        if(updateCounter$i==3) {
          value3 <<- partialsum
          return(paste("Partial result", value3))
        } 
        if(updateCounter$i<3){
          return()
        }
        if(updateCounter$i==0){
          return()
        }
        if(updateCounter$i>3) {
        display1 <- paste("Partial result", value3)
        display2 <- paste("Total result", partialsum)  
        twolinesdisplay<<- HTML(paste(display1, display2, sep = '<br/>'))
        return(twolinesdisplay)

        } 
      })
  # # Print the table on mail panel
  output$example <- DT::renderDataTable({  return(values())  })
}

shinyApp(ui = ui, server = server)

When interactions equals 3 is displayed the sum of column 3, more than 3 displays the partial sum and the current total sum. Each time that the restart button is clicked, table is reset to default values and process starts again. But the interaction counter does not reset to zero.

I have tried to use the idea of this post but without success. Any suggestion?

Answer 1

Is this what you are looking for?

library(shiny)
library(DT)

ui <- fluidPage(
  sidebarPanel(numericInput("c1", "Example", NA),
               tags$p(actionButton("update", "Update")),
               tags$p(actionButton("reset", "Clear")),
               tags$p(actionButton("restart", "Restart")),
               textOutput("count"),
               htmlOutput("display")
  ),
  mainPanel(  DT::dataTableOutput("example"))
)

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

  # stores the current data frame
  values <- reactiveVal(data.frame(A = 1, B = 2, C = 3))

  # update values table on button click
  observeEvent(input$update,{

    old_values <- values()

    A_new <- input$c1
    B_new <- A_new + 2
    C_new <- A_new + B_new

    new_values <- data.frame(A = A_new, B = B_new, C = C_new)

    # attach the new line to the old data frame here:
    new_df <- rbind(old_values, new_values)

    #store the result in values variable
    values(new_df)

    #reset the numeric input to NA  
    updateNumericInput(session, "c1", "Example", NA)

  })

  #Delete last row 
  deleteEntry <- observeEvent(input$reset,{
    values( values()[-nrow(values()),])
  })


  updateCounter <- reactiveValues(i = 0)

  ##This output value must be reset to 0    
  output$count <- renderText({
    paste0("Iteractions: ", updateCounter$i)
  })

  observe({
    input$update
    isolate({
      updateCounter$i <- updateCounter$i + 1
    })
  })

  observe({
    input$reset
    isolate(updateCounter$i <- updateCounter$i - 1)
  })

  #Restart
  defaultvalues <- observeEvent(input$restart, {
    isolate(updateCounter$i == 0)
    values( values()[1,])
    updateCounter$i <- 0
  }) 

  Total <- reactive({ colSums(values()[3]) })

  output$display  <- renderText({
    partialsum <-Total()
    if(updateCounter$i==3) {
      value3 <<- partialsum
      return(paste("Partial result", value3))
    } 
    if (updateCounter$i < 3){
      return()
    }
    if (updateCounter$i == 0){
      return()
    }
    if(updateCounter$i > 3) {
      display1 <- paste("Partial result", value3)
      display2 <- paste("Total result", partialsum)  
      twolinesdisplay<<- HTML(paste(display1, display2, sep = '<br/>'))
      return(twolinesdisplay)

    } 
  })
  # # Print the table on mail panel
  output$example <- DT::renderDataTable({ values() })
}

shinyApp(ui, server)

It seems like

updateCounter$i <- 0

works while

updateCounter <- reactiveValues(i = 0)

does not.