Delay on sliderinput - r

Question

Is there a way to make the sliderInput wait for a couple seconds before it changes its corresponding input$ variable? I have a bar that is controlling a graph that needs to re-render upon the value change. I'm aware of the workaround with a submit button, I'm looking to avoid needing that.

Answer 1

debounce is made for this, and is simpler. Modifying previous answerer's code:
library(shiny)
library(magrittr)
shinyApp(
server = function(input, output, session) {
d_mean <- reactive({
input$mean
}) %>% debounce(1000)
output$plot <- renderPlot({
x <- rnorm(n=1000, mean=d_mean(), sd=1)
plot(density(x))
})
},
ui = fluidPage(
sliderInput("mean", "Mean:", min = -5, max = 5, value = 0, step= 0.1),
plotOutput("plot")
)
)

Answer 2

You can use invalidateLater. It can be done in a naive but concise way:
library(shiny)
shinyApp(
server = function(input, output, session) {
values <- reactiveValues(mean=0)
observe({
invalidateLater(3000, session)
isolate(values$mean <- input$mean)
})
output$plot <- renderPlot({
x <- rnorm(n=1000, mean=values$mean, sd=1)
plot(density(x))
})
},
ui = fluidPage(
sliderInput("mean", "Mean:", min = -5, max = 5, value = 0, step= 0.1),
plotOutput("plot")
)
)
Problem with this approach is that you can still trigger execution when changing slider input and invalidate event is fired. If thats the problem you try a little bit more complex approach where you check if values changed and how many time value has been seen.
library(shiny)
library(logging)
basicConfig()
shinyApp(
server = function(input, output, session) {
n <- 2 # How many times you have to see the value to change
interval <- 3000 # Set interval, make it large so we can see what is going on
# We need reactive only for current but it is easier to keep
# all values in one place
values <- reactiveValues(current=0, pending=0, times=0)
observe({
# Invalidate
invalidateLater(interval, session)
# Isolate so we don't trigger execution
# by changing reactive values
isolate({
m <- input$mean
# Slider value is pending and not current
if(m == values$pending && values$current != values$pending) {
# Increment counter
values$times <- values$times + 1
loginfo(paste(values$pending, "has been seen", values$times, "times"))
# We've seen value enough number of times to plot
if(values$times == n) {
loginfo(paste(values$pending, "has been seen", n, "times. Replacing current"))
values$current <- values$pending
}
} else if(m != values$pending) { # We got new pending
values$pending <- m
values$times <- 0
loginfo(paste("New pending", values$pending))
}
})
})
output$plot <- renderPlot({
x <- rnorm(n=1000, mean=values$current, sd=1)
plot(density(x))
})
},
ui = fluidPage(
sliderInput("mean", "Mean:", min = -5, max = 5, value = 0, step= 0.1),
plotOutput("plot")
)
)