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)

please have a look at the tutorials https://shiny.rstudio.com/tutorial/ as you seem to be using `output$text2` and `output$text` inside the server incorrectly — Pork Chop, Jul 27 '18 at 08:12

Florian · Accepted Answer · 2018-07-27T08:16:36.717

5

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)

edited Jul 27 '18 at 08:16

answered Jul 27 '18 at 08:10

Florian

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love it! also just found a way to calculate the difference using https://stackoverflow.com/questions/40997817/reactive-variables-in-shiny-for-later-calculations. Thanks!! – frank Jul 27 '18 at 08:27
Great, glad I could help! Also, this was just a quick answer, but what might be slightly cleaner is setting the `reactiveVal` only to the numeric value, and creating the actual text in the `rendertext` statement. So `rv_text2(sum(v))` and `output$text2 <- renderText({paste("Slider Sum:",rv_text2())})`. hat make sit easier to use the number in subsequent calculations – Florian Jul 27 '18 at 08:32
Also, please consider [accepting the answer](https://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) if it solved your issue, thanks. – Florian Jul 27 '18 at 08:32
Thanks for the tips. I have a long way to go still! As an aside, my actual program has 16 variables in it with sliders, and implementing your suggestion, does not work as well. I will keep debugging to see, but I love it!! – frank Jul 27 '18 at 10:07
Hi @alex, you could potentially also use a for-loop to reset the inputs. You can even get their values dynamically. Not sure if that last part is helpful to you, but with 16 sliders, it sounds like it might be ;) See e.g. [here](https://stackoverflow.com/questions/50795355/how-to-save-selected-checkbox-ids-from-checkboxgroupinput-and-how-to-extract/50797226#50797226) – Florian Jul 27 '18 at 10:31

Reset sliders in RShiny

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