Make upper value of R shiny slider range always be higher than lower value [duplicate]

I have a slider that looks like this:

The code for the slider is as follows:

UI:

fluidRow(column(12,
                    uiOutput("slider")))

SERVER:

mindate <- "2011-04-01"
maxdate <- "2017-03-31"

    output$slider <- renderUI({
        sliderInput("timeperiod", "Time Period:",
                    min=as.Date(mindate, origin='1970-01-01'),
                    max=as.Date(maxdate, origin='1970-01-01'),
                    value=c(as.Date(mindate, origin='1970-01-01'),
                            as.Date(maxdate, origin='1970-01-01')),
                    timeFormat='%b-%y', dragRange = TRUE, width='700px')
      })

Currently if you move the slider inputs they can be put as the same value like this:

Is there a way so that I can always keep the upper value of the slider a certain amount of ticks above the bottom value of the slider?

Pork Chop

You can add 31 days to the datetime object you have, however that is crude. Other ways of adding a month you can have a look here: Add a month to a Date

  observeEvent(input$timeperiod,{
    if(input$timeperiod[1] == input$timeperiod[2]){
      updateSliderInput(session, "timeperiod", value=c(input$timeperiod[1],(input$timeperiod[1]+31)))
    }
  })

Edit: To use the dates later on You can access the dates via the sliderMonth$Month reactive I've created

rm(list=ls())
library(shiny)

monthStart <- function(x) {
  x <- as.POSIXlt(x)
  x$mday <- 1
  as.Date(x)
}

mindate <- "2011-04-01"
maxdate <- "2017-03-31"

ui <- fluidPage(
  mainPanel(uiOutput("slider"),textOutput("SliderText"))
)

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

  observeEvent(input$timeperiod,{
    if(input$timeperiod[1] == input$timeperiod[2]){
      updateSliderInput(session, "timeperiod", value=c(input$timeperiod[1],(input$timeperiod[1]+31)))
    }
  })

  output$slider <- renderUI({
    sliderInput("timeperiod", "Time Period:",
                min=as.Date(mindate, origin='1970-01-01'),
                max=as.Date(maxdate, origin='1970-01-01'),
                value=c(as.Date(mindate, origin='1970-01-01'),as.Date(maxdate, origin='1970-01-01')),
                timeFormat='%b-%y', dragRange = TRUE, width='700px')
  })

  sliderMonth <- reactiveValues()
  observeEvent(input$timeperiod,{
    full.date <- as.POSIXct(input$timeperiod, tz="GMT")
    sliderMonth$Month <- as.character(monthStart(full.date))
  })
  output$SliderText <- renderText({sliderMonth$Month})
}
shinyApp(ui, server)

来源：https://stackoverflow.com/questions/43785070/make-upper-value-of-r-shiny-slider-range-always-be-higher-than-lower-value

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Shiny

slider