Reset sliders in RShiny

Question

I am new to shiny, and am making an app where a user adjusts 3 sliders. Output is the total change of the 3 sliders in % form, and the difference from the initial form.

I added a 'reset' button so that I can change the sliders all back to 0, but it is not working.

I tried looking R shiny: reset plot to default state, and Reset inputs with reactive app in shiny, to no avail. I tried a piece of code:

  observeEvent(input$reset,{
    input$Var1=0 
    return(input$Var1)
  })

to adjust a single slider and set it to 0, then return this value, also to no avail. Any suggestions?

My full code is :

library(shiny)

ui=fluidPage(
  titlePanel("Sum of Sliders"),
  fluidRow(
    column(2,
           sliderInput("Var1", "Slider1:",
                       min = -100, max = 100,
                       value = 0),
           sliderInput("Var2", "Slider2:",
                       min = -100, max = 100,
                       value = 0),
           sliderInput("Var3", "Slider3:",
                       min = -100, max = 100,
                       value = 0),
           submitButton("Submit"),
           actionButton("reset", "Reset")
    ),
    column(6,
           verbatimTextOutput("text"),
           verbatimTextOutput("text2"),
           verbatimTextOutput("change")
    )
  )
)

server=function(input, output) {
  observeEvent(input$reset,{
    input$Var1=0 
    return(input$Var1)
  })

  output$text <- renderText({
    paste("Starting Value:", 0)
  })

  output$text2= renderText({
    v=rep(0,3)
    v[1]= input$Var1/100
    v[2]= input$Var2/100
    v[3]= input$Var3/100
    paste("Slider Sum:", sum(v))
  })

  output$change <- renderText({
    paste("Difference is:", output$text2-output$text)
  })
}

shinyApp(ui, server)

Answer 1

To change an existing input, you can use updateSliderInput. Also, since you included a submitButton, I assume you want the changes to only apply when you click that button. It is probably easiest to use reactiveVal's to get the desired behavior. A working example is given below, creating output$change is left as an exercise to the reader ;) hope this helps!

library(shiny)

ui=fluidPage(
  titlePanel("Sum of Sliders"),
  fluidRow(
    column(2,
           sliderInput("Var1", "Slider1:",
                       min = -100, max = 100,
                       value = 0),
           sliderInput("Var2", "Slider2:",
                       min = -100, max = 100,
                       value = 0),
           sliderInput("Var3", "Slider3:",
                       min = -100, max = 100,
                       value = 0),
           actionButton('submit','Submit'),
           actionButton("reset", "Reset")
    ),
    column(6,
           verbatimTextOutput("text"),
           verbatimTextOutput("text2")
    )
  )
)

server=function(input, output, session) {
  observeEvent(input$reset,{
    updateSliderInput(session,'Var1',value = 0)
    updateSliderInput(session,'Var2',value = 0)
    updateSliderInput(session,'Var3',value = 0)
  })

  rv_text1 <- reactiveVal()
  rv_text2 <- reactiveVal()

  observeEvent(input$submit,{
    rv_text1(paste("Starting Value:", 0))
    v=rep(0,3)
    v[1]= input$Var1/100
    v[2]= input$Var2/100
    v[3]= input$Var3/100
    rv_text2(paste("Slider Sum:", sum(v)))

  })

  output$text <- renderText({rv_text1()})
  output$text2 <- renderText({rv_text2()})

}

shinyApp(ui, server)