R Shiny Debounce with reactiveValues and observeEvent / R input debounce - r

I am currently trying in vain to use the debounce function in Shiny to delay my input a bit. The goal is to have the renderText not fire every few milliseconds, but only after 2 second intervals.
I tried to implement the following solution. Thereby I absolutely need the reactiveValues and observeEvent functions. Other solutions here never take this combination into account and I am currently stuck. My example code is shortened. In reality the variable name1$data is still used by different functions and the RenderText accesses different variables.
if (interactive()) {
ui <- fluidPage(
textInput("IText1", "Input i want to slow down"),
textOutput("OName")
)
server <- function(input, output, session) {
Name1 <- reactiveValues()
observeEvent(input$IText1, {Name1$data <- input$IText1})
#Solutions on stackoverflow
#Just causes errors for me
#Name1$t <- debounce(Name1$data, 2000)
output$OName <- renderText({
Name1$data
})
}
shinyApp(ui, server)
}
Thank you very much for any hint!

Normally we debounce reactive conductors (reactive({......})):
ui <- fluidPage(
textInput("IText1", "Input i want to slow down"),
textOutput("OName")
)
server <- function(input, output, session) {
Name1 <- reactive({
input$IText1
})
Name1_d <- debounce(Name1, 2000)
output$OName <- renderText({
Name1_d()
})
}
shinyApp(ui, server)
EDIT
Or you need
server <- function(input, output, session) {
Name1 <- reactiveValues()
observe({
invalidateLater(2000, session)
Name1$data <- isolate(input$IText1)
})
output$OName <- renderText({
Name1$data
})
}

Related

How to efficiently subset a dataframe in R Shiny?

In the below example code I reactively subset the mtcars dataframe inside the renderPlot() function. However, in my larger App with many render functions in the server section I am having to repeat the same rv$x[1:input$samples], etc., over and over in many places. How would I apply this subsetting instead "at the top", into the rv <- reactiveValues(...) function itself or equivalent "master function"? I tried subsetting inside the reactiveValues() and got the message "Warning: Error in : Can't access reactive value 'samples' outside of reactive consumer. Do you need to wrap inside reactive() or observer()?" I assumed incorrectly that the reactiveValues() function is a "reactive consumer".
If someone can answer this basic understanding question, please explain the logic for correctly subsetting "at the top" because I am getting very embarrassed by my repeated questions about Shiny reactivity.
library(shiny)
ui <- fluidPage(
sliderInput('samples','Nbr of samples:',min=2,max=32,value=16),
plotOutput("p")
)
server <- function(input, output, session) {
rv <- reactiveValues(
x = mtcars$mpg,
y = mtcars$wt
)
output$p <- renderPlot({plot(rv$x[1:input$samples],rv$y[1:input$samples])})
}
shinyApp(ui, server)
There are multiple ways you can handle this.
Here is one way to create new subset reactive values inside observe.
library(shiny)
ui <- fluidPage(
sliderInput('samples','Nbr of samples:',min=2,max=32,value=16),
plotOutput("p")
)
server <- function(input, output, session) {
rv <- reactiveValues(
x = mtcars$mpg,
y = mtcars$wt
)
observe({
rv$x_sub <- rv$x[1:input$samples]
rv$y_sub <- rv$y[1:input$samples]
})
output$p <- renderPlot({plot(rv$x_sub,rv$y_sub)})
}
shinyApp(ui, server)
I'd use reactiveValues only if you need them to be modified in different places.
reactive is shiny's basic solution for this:
library(shiny)
library(datasets)
ui <- fluidPage(
sliderInput(
'samples',
'Nbr of samples:',
min = 2,
max = 32,
value = 16
),
plotOutput("p")
)
server <- function(input, output, session) {
reactive_mtcars <- reactive({mtcars[1:input$samples,]})
output$p <- renderPlot({
plot(reactive_mtcars()$mpg, reactive_mtcars()$wt)
})
}
shinyApp(ui, server)

Updating non-reactive values in R Shiny

I have the following example:
library(shiny)
ui <- fluidPage(
textOutput("out"),
actionButton("plusX", "Increase X"),
actionButton("redraw", "redraw")
)
server <- function(input, output, session) {
x <- 0
observeEvent(input$plusX, {x <<- x+1})
output$out <- renderText({
input$redraw
x
})
}
shinyApp(ui, server)
Is this considered an anti-pattern in Shiny to modify a non-reactive variable in this way? Obviating the super assignment which can be problematic by itself.
I know this could be done, for example with a reactiveVal to store X, and isolate to obtain a similar result. This second way seems clearer and that would be my usual choice, but I was wondering if there any caveats in the first one, or it is possible way of doing that.
library(shiny)
ui <- fluidPage(
textOutput("out"),
actionButton("plusX", "Increase X"),
actionButton("redraw", "redraw")
)
server <- function(input, output, session) {
x <- reactiveVal(0)
observeEvent(input$plusX, {x(x()+1)})
output$out <- renderText({
input$redraw
isolate(x())
})
}
shinyApp(ui, server)
In this example there is no important difference between both codes as you are not using the benefit of ReactiveVal.
The benefit of ReactiveVal is that it has a reactive nature and thus can interact with other reactive elements.
Try for example to add a table to your code that depends on x:
output$tab <- renderTable({data.frame(y = x)})
(x() in the case of ReactiveVal)
The difference you will see that in the case of ReactiveVal the table automatically updates with plusX whereas in the case of the regular variable it does not update.

How to update reactive output inside a for loop in R shiny

I'm new to Shiny and have hit a problem I can't find an answer for. Basically, I have a Shiny app that does some long calculations in a loop and I want it to output a "progress report" every few iterations. However, even though I reassign my reactive variable within the loop, the output doesn't update until the loop (or entire function?) has finished.
Here is a simplified test case of what I mean:
library(shiny)
# Basic interface
ui <- fluidPage(
actionButton("run", "Run"),
textOutput("textbox")
)
# Basic server with loop
server <- function(input, output) {
textvals=reactiveValues(a=0)
observeEvent(input$run, {
for(i in 1:10){
textvals$a=i # Expect output to update here, but doesn't
Sys.sleep(0.1) # Slight pause so isn't instantaneous
}
})
output$textbox <- renderText({
textvals$a
})
}
# Run the application
shinyApp(ui = ui, server = server)
What I would expect is that the display would update 1, 2, 3, ... 10 as the loop executes. Instead, it just jumps straight from 0 to 10. How can I force an update partway through the loop?
Thank you.
With using invalidateLater you can get something closed to what you want. Not the shortest way to do it I think, but it may help you to find a better solution.
library(shiny)
# Basic interface
ui <- fluidPage(
actionButton("run", "Run"),
textOutput("textbox")
)
# Basic server with loop
server <- function(input, output, session) {
textvals <- reactiveVal(0)
active <- reactiveVal(FALSE)
output$textbox <- renderText({
textvals()
})
observe({
invalidateLater(1000, session)
isolate({
if (active()) {
textvals(textvals() + 1)
if (textvals() > 9) {
active(FALSE)
}
}
})
})
observeEvent(input$run, {
active(TRUE)
})
}
# Run the application
shinyApp(ui = ui, server = server)
By the way, reactive and for loops don't really get on well. This may help : https://gist.github.com/bborgesr/e1ce7305f914f9ca762c69509dda632e

How to make an operation uninterruptible in R shiny

In my shiny app I have a output which should update itself continuously. But whenever I execute a long-running calculation, the output is just paused. My question is: how to make the output runs continuously and uninterruptible?
Please see the short demo below:
The clock refreshes every one second, but if I click the button which runs for 5 seconds, the clock is paused.
library(shiny)
ui <- fluidPage(
actionButton("button","Expensive calcualtion(takes 5 seconds)"),
tags$p("Current Time:"),
textOutput("time"),
tags$p("Result from clicking button:"),
textOutput("result")
)
server <- function(input, output, session) {
output$time <- renderText({
invalidateLater(1000)
as.character(Sys.time())
})
observeEvent(input$button,{
Sys.sleep(5)
output$result <- renderText(runif(1))
})
}
shinyApp(ui, server)
I tried to use future and promises to make the long-running process runs asynchronously, but it doesn't work. Where is wrong? And is there a better way for achieving this purpose?
library(shiny)
library(future)
library(promises)
plan("multisession")
ui <- fluidPage(
actionButton("button","Expensive calcualtion(takes 5 seconds)"),
tags$p("Current Time:"),
textOutput("time"),
tags$p("Result from clicking button:"),
textOutput("result")
)
server <- function(input, output, session) {
output$time <- renderText({
invalidateLater(1000)
as.character(Sys.time())
})
process <- eventReactive(input$button,{
future({
Sys.sleep(5)
runif(1)
})
})
output$result <- renderText(process())
}
shinyApp(ui, server)
Any help is appreciated!
Thanks #Shree for pointing out the solution. After reading the response from Joe Cheng. It seems like the key is to:
Hide the async operation from Shiny by not having the promise be the last expression.
The problem is resolved by creating a reactive value and assign the promise to it in observeEvent as the side effect.
server <- function(input, output, session) {
output$time <- renderText({
invalidateLater(1000)
as.character(Sys.time())
})
process <- reactiveVal()
observeEvent(input$button,{
output$isbusy <- renderText("busy") # a simple busy indicator
future({
Sys.sleep(5)
runif(1)
}) %...>%
process()
# Hide the async operation from Shiny by not having the promise be the last expression
NULL # important
})
output$result <- renderText({
output$isbusy <- renderText("") # a simple busy indicator
process()
})
}
Your problem is that Sys.sleep() suspends the execution of R expression. You can use things like the delay() function from shinyjs
library(shiny)
library(shinyjs)
ui <- fluidPage(
useShinyjs(), #You have to add this.
actionButton("button","Expensive calcualtion(takes 5 seconds)"),
tags$p("Current Time:"),
textOutput("time"),
tags$p("Result from clicking button:"),
textOutput("result")
)
server <- function(input, output, session) {
timer <- reactiveTimer(500)
current_time <- reactive({
timer()
as.character(Sys.time())
})
output$time <- renderText(current_time())
observeEvent(input$button,{
delay(5000, output$result <- renderText("result"))
})
}
shinyApp(ui, server)

Passing data within Shiny Modules from Module 1 to Module 2

I dont have a reproducible example as the question is more on how modules work. I am trying to understand how to pass some reactive function from one module to the next. I have received replies in the past about using ObserveEvent but they have not seem to work when I am using the reactive value in one module to perform some other operation in another module
module1 <- function(input, output, session){
data1<-reactive({
#some reacttive funcion that produces an output
})
data2<-reactive({
#some reacttive funcion that produces another output
})
return(list(data1,data2))
}
module2 <- function(input, output, session,data1){
observe( data1(), {
#perform some other functions here using data1().e.g reading or parsing data
})
}
So basically I have a module1 that returns two outputs from data1 and data2
I want to use the value of data1 in module 2 and perform some new operation using that value.
I have looked at other answers to similar questions here but I still dont understand them. If someone can help me explain this concept more clearly that would be of great help
thanks for your help
One possibility is passing the output from one module to the other at construction time. This allows hierachic relationships between modules. There is also the possibility to create memory that is shared between two modules which I will not cover in this answer.
reactiveValues
Here i created an inputModule and an outputModule. The inputModule recieves two textinputs by the user and the output module displays them via verbatimTextOutput. The inputModule passes the user submitted data to the output module as a reactiveValues object called ImProxy (input module proxy). The outputModule accesses the data just like a list (ImProxy$text1, ImProxy$text2).
library(shiny)
inputModuleUI <- function(id){
ns <- NS(id)
wellPanel(h3("Input Module"),
textInput(ns('text1'), "First text"),
textInput(ns('text2'), "Second text"))
}
inputModule <- function(input, output, session){
vals <- reactiveValues()
observe({vals$text1 <- input$text1})
observe({vals$text2 <- input$text2})
return(vals)
}
outputModuleUI <- function(id){
wellPanel(h3("Output Module"),
verbatimTextOutput(NS(id, "txt")))
}
outputModule <- function(input, output, session, ImProxy){
output$txt <- renderPrint({
paste(ImProxy$text1, "&", ImProxy$text2)
})
}
ui <- fluidPage(
inputModuleUI('IM'),
outputModuleUI('OM')
)
server <- function(input, output, session){
MyImProxy <- callModule(inputModule, 'IM')
callModule(outputModule, 'OM', MyImProxy)
}
shinyApp(ui, server)
This approach can be used with observe or observeEvent as well.
list(reactive)
If you want to use reactive rather than reactiveValues, the following adaptiation of the above code can be used. You can leave the ui functions as they are.
inputModule <- function(input, output, session){
list(
text1 = reactive({input$text1}),
text2 = reactive({input$text2})
)
}
outputModule <- function(input, output, session, ImProxy){
output$txt <- renderPrint({
paste(ImProxy$text1(), "&", ImProxy$text2())
})
}
shinyApp(ui, server)
reactive(list)
Again, this will give the same functionality for the app but the proxy pattern is slightly different.
inputModule <- function(input, output, session){
reactive(
list(
text1 = input$text1,
text2 = input$text2
)
)
}
outputModule <- function(input, output, session, ImProxy){
output$txt <- renderPrint({
paste(ImProxy()$text1, "&", ImProxy()$text2)
})
}
shinyApp(ui, server)

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