Customize labels to an exponential text format on

Question

I'm using a vertical noUiSliderInput in my app

I would like to replace the labels, defined in pips of noUiSliderInput from regular numbers to text strings that are 10^x, where x is the original label.

The slider has the following properties (some background info):

• It is build as uiOutput in my server
• It is linear, but is next to a logarithmic ggplot. Therefore I made the sliders values actually the "power numbers" to run from for instance -1 to 3 if my actual data has a range of 0.1 (10^-1) to 1000 (10^3).
• This way the linear slider can follow the logarithmic plot
• min and max depend on the range of values in the datafile the user opens from a selectInput menu, which loads the file, and calculates new min and max for the slider, and causes it to rerender.

I know it should most likely be achieved with javascript, but so far my attempts don't even come close to have any effect.

I saw this example here for a regular slider to replace the label with words, but changing to 10 to the power superscript is another story, and I am so far unable to target the noUislider with the example. SO question

SERVER File

server <- function(input, output, session) {
  values <- reactiveValues( 
    minimum = 1
  )

  observeEvent(input$Button1, { 
    values$minimum <- sample(1:5, 1)
  })

  observe({ values$maximum <- values$minimum + 5})

  output$sliderout <- renderUI({ 
    noUiSliderInput(
      inputId = "YOUR_SLIDER_ID", 
      label = "Slider vertical:",
      min = values$minimum, 
      max = values$maximum,
      step = 0.1,
      value = values$minimum,
      orientation = "vertical",
      pips = list(
        mode = "range",
        density = 10
      ),
      width = "100px", height = "300px"
    )})
  output$res2 <- renderPrint(input$noui2)
}

UI file

library(shiny)
library(shinyWidgets)

ui <- fluidPage(
 # includeScript("slider.js"), ## line to open file with javascript

  tags$br(),
  div(class = 'myslider', uiOutput('sliderout')),
  actionButton(inputId = 'Button1', label = 'Change slider'),
  verbatimTextOutput(outputId = "res2")
)

Answer 1

This is what I've managed to achieve. There's only one problem: 1000 is rendered as 1000.000000000002. I don't know how to deal with that.

library(shiny)
library(shinyWidgets)
library(shinyjs)

js <- paste(
  "var slider = document.getElementById('noui').noUiSlider;",
  "slider.updateOptions({", 
  "  format: wNumb({", 
  "    encoder: function(x){return Math.pow(10,x);}", 
  "  })", 
  "});",
  "slider.pips({",
  "  mode: 'range',", 
  "  density: 2,", 
  "  format: {", 
  "    to: function(x){return '10^' + x;}",
  "  }",
  "});",
  sep = "\n"
)

ui <- fluidPage(
  useShinyjs(),
  tags$br(),

  noUiSliderInput(
    inputId = "noui", label = "Slider vertical:",
    min = -2, max = 4, step = 1,
    value = 0, margin = 100,
    orientation = "vertical", 
    width = "300px", height = "300px"
  ),

  verbatimTextOutput(outputId = "res")

)

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

  output$res <- renderPrint(input$noui)

  observeEvent(input$noui, {
    runjs(js)
  }, once = TRUE)

}

shinyApp(ui, server)

EDIT

I have not found how to get HTML pips values with the help of the format option. Here is a way to get 10^x with superscripts:

var pipsValues = $('.noUi-value');
pipsValues.each(function(){$(this).html('10<sup>'+$(this).attr('data-value')+'</sup>')});

That is, the full JS code is:

js <- paste(
  "var slider = document.getElementById('noui').noUiSlider;",
  "slider.updateOptions({", 
  "  format: wNumb({", 
  "    encoder: function(x){return parseFloat(Math.pow(10,x).toPrecision(2));}", 
  "  })", 
  "});",
  "slider.pips({",
  "  mode: 'range',", 
  "  density: 2", 
  "});",
  "var pipsValues = $('.noUi-value');",
  "pipsValues.each(function(){$(this).html('10<sup>'+$(this).attr('data-value')+'</sup>')});",
  sep = "\n"
)

EDIT 2

Here is an app which deals with the case when min, max and value are reactive values. The idea is to avoid renderUI: the app starts with an initial slider and these three values are updated by Javascript, with the help of the updateOptions method.

library(shiny)
library(shinyWidgets)
library(shinyjs)

js <- function(Min, Max, Start){
  sprintf(paste(
    "var slider = document.getElementById('noui').noUiSlider;",
    "slider.updateOptions({",
    "  start: %s,",
    "  range: {min: %s, max: %s},",
    "  format: wNumb({", 
    "    encoder: function(x){return parseFloat(Math.pow(10,x).toPrecision(2));}", 
    "  })", 
    "});",
    "var pipsValues = $('.noUi-value');",
    "pipsValues.each(function(){$(this).html('10<sup>'+$(this).attr('data-value')+'</sup>')});",
    sep = "\n"
  ), Start, Min, Max)
}

ui <- fluidPage(
  useShinyjs(),

  actionButton("btn", "Sample"),

  tags$br(),

  noUiSliderInput(
    inputId = "noui", label = "Slider vertical:",
    min = -2, max = 4, step = 1,
    value = 0, margin = 100, 
    pips = list(mode="range", density=2),
    orientation = "vertical", 
    width = "300px", height = "300px", 
    behaviour = "tap"
  ),

  verbatimTextOutput(outputId = "res")

)

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

  Values <- eventReactive(input$btn, {
    Min <- sample(-5:5, 1)
    Max <- Min + 6
    Start <- sample(Min:Max, 1)
    list(min = Min, max = Max, start = Start)
  }, ignoreNULL = FALSE)

  observe({
    if(!is.null(input$noui)){
      values <- Values()
      runjs(js(values$min,values$max,values$start))
    }
  })

  output$res <- renderPrint(input$noui)

}

shinyApp(ui, server)