I want to somehow make two inputs equal to one another when I press an Actionbutton. I have several tabs in my Shiny Dashboard and in some of the tabs there are repeat data inputs. For example, in tab 1 we have an input for AGE, we have the same input in tab 2. I want to make it such that if I input a value for age and click "run" (an Actionbutton), then it automatically makes the age in the other tab equal to the one in the current tab.
I'm really really new to using Shiny, so I made a few attempts at using reactive commands, but I'm not sure why it isn't working:
reactive(
if(input$runbutton==0){
input$numeric1=input$numeric2
})
That code has no effect, it doesn't even return an error.
You should use updateNumericInput() to change the value of an input. Also it makes more sense to use observeEvent() to track button presses. Here a simple sample application
ui <- fluidPage(
numericInput("numeric1","in1",1),
numericInput("numeric2","in2",2),
actionButton("runbutton", "set equal")
)
server <- function(input, output, session) {
observeEvent( input$runbutton, {
updateNumericInput(session, "numeric1", value=input$numeric2)
})
}
shinyApp(ui=ui, server=server)
Related
TL;DR: observeEvent is only working on the first instance, but not subsequent.
Explanation:
In a small shiny app below, I dynamically build a URL based on user input, which points to the corresponding pre-rendered "timer" gif images I have hosted on GH. In this shiny app code below, observeEvent works great to pull the sliderInput value (e.g. 5sec), build a URL, and then clicking 'go' will show the timer using a clever shinyjs package. However, if I do not change the input (still 5sec), clicking go doesn't rebuild the image. If I change the value to a different number (4sec), it will show the correct gif. If I change back to the original number (5sec), no gif. If I go to a new number (3sec), correct gif. If I print the value of input$time or of rv$time in my observeEvent, then each of those values are updating correctly (both print the corresponding value).
Goal: to show the gif that corresponds to the input$time upon each update of input$go
Reprex:
library(shiny)
library(tidyverse)
library(glue)
library(shinyjs)
# Define UI
ui <- navbarPage(title = "Reprex",
## RHYME TIME -----
tabPanel("Time",
useShinyjs(),
sidebarLayout(
sidebarPanel(
sliderInput("time",
"Seconds",
min = 3,
max = 10,
value = 5
),
actionButton(inputId = "go",
label = "Go"),
),
mainPanel(
HTML("<center>"),
shinyjs::hidden(htmlOutput("simple_timer")),
HTML("</center>")
)
)
)
)
# Define server logic
server <- function(input, output, session) {
#a container to store my time var
rv <- reactiveValues(
time = 0
)
#the event that is triggered by input$go getting clicked
observeEvent(input$go, {
rv$time <- input$time #this should update rv$time after go is clicked
shinyjs::show("simple_timer") #this is the clever package with simple show/hide funs
})
#the reactive text that generates my HTML
output$simple_timer <- renderText({
glue::glue('<img src ="https://github.com/matthewhirschey/time_timer/raw/main/data/{rv$time}_sec.gif",
align = "center",
height="50%",
width="50%">')
})
}
# Run the application
shinyApp(ui = ui, server = server)
There are a couple of issues with your code:
renderText won't refire if you press input$go again (w/o changing the slider). Becasue the idea is that observer/render fires whenever their reactives change. As your renderText depends on rv$time which does not change when input$time does not change, the render function is not fired on subsequent button presses. This can be remedied by including input$go in the render function setting an additional dependency on the button.
This will not, however, solve your problem, because the browser uses caching. It sees that the <img> tag did not change (same src), thus it does not reload the picture. To circumvent that you can use the trick from Disable cache for some images by adding a timestamp to the src.
To make a long story short, this code does the trick:
output$simple_timer <- renderText({
input$go # make code dependent on the button
# add `?timestamp=<timestamp>`to the src URL to convince the browser to reload the pic
glue::glue('<img src ="https://github.com/matthewhirschey/time_timer/raw/main/data/{rv$time}_sec.gif?timestamp={Sys.time()}",
align = "center",
height="50%",
width="50%">')
})
I am building an application that is meant to help students understand sampling. The application allows students to choose a sample size and then see how many 1's they get, given some probability. When sample size is small (i.e., 1), it often occurs that the same value (either a 0 or 1) is sampled multiple times in a row. However, if students click the action button to re-sample and get the same value as in their last random draw, I'm having trouble making it visually clear that the value has updated (i.e., that something happened, even though it gave the same result as before). Ideally, I would like the action button click to cause this field on the main panel to go blank for a fraction of a second and then display the new value.
I have tried using Sys.sleep to get the system to sleep for a second before proceeding, but this does not work. I can get it to (sort of) work by trying to print something else in the same output field before using Sys.sleep, but I feel like there must be an easier way.
ui <- fluidPage(
titlePanel("Example"),
sidebarLayout(
sidebarPanel(
actionButton("run", "Pick a number (0 or 1)")),
mainPanel(
h4("Your Number!"),
textOutput("result")
)
)
)
server <- function(input, output,session) {
observeEvent(input$run, {
x <- sample(c(0,1),size=1,prob=c(.5,.5),replace=T)
###Including these commented lines achieves what I want,
###but doesn't seem very elegant:
# output$result <- renderText({
# print("something")
# })
Sys.sleep(1)
output$result <- renderText({
paste("You got the number ",x)
})
})
}
shinyApp(ui, server)
I'm fairly new to R Shiny but am stuck with the following problem for some time now and hope you can provide some help:
I try to refresh a plot in R shiny that should be refreshed if either a new input argument is entered OR an action button is pressed. This should be straightforward, but unfortunately I can't solve it, despite googling/reading instructions for some time. Any advice would be recommended. Any solutions on the web seem to put the whole renderplot function inside the observeEvent function, but I also need the renderplot in addition outside of it to account for the possibility of just entering inputs without pressing the action button.
I have no trouble creating a (render)plot that either exclusively is refreshed when entering a new input or exclusively refreshed when pressing a button.
However when doing both at the same I fail: I first tried to copy the renderplot function including the resulting output twice one time within an observeEvent function (to account for clicking the action button) and one time outside of an observeEvent (to account for only refreshing the inputs to the plot) but this leads only to a greyed out graph that refreshes after ~10 seconds delay when pressing the action button. I imagine adding the reactive click input generated from clicking the action button directly to the renderplot outside of observe event , but so far I couldn't get it to run. Any recommendations would be much appreciated.
Thank you in advance.
Like this?:
Edit: No need to pass the selectInput to the reactive Vals.. this does the same:
library(shiny)
ui <- fluidPage(
sidebarLayout(
sidebarPanel(
selectInput(inputId="select", label="title", choices=LETTERS[1:3], selected = "A"),
actionButton(inputId="btn", label="refresh")
),
mainPanel(
plotOutput("scatterPlot")
)
)
)
server <- function(input, output) {
plotSettings <- reactiveValues()
observeEvent(c(input$btn, input$select), {
plotSettings$values <- runif(100,1,100)
# plotSettings$title <- input$select
}, ignoreNULL = FALSE)
output$scatterPlot <- renderPlot({
plot(plotSettings$values, main=input$select)
})
}
shinyApp(ui = ui, server = server)
Note: After coming up with the answer I reworded the question to make if clearer.
Sometimes in a shiny app. I want to make use of a value selected by the user for a widget, as well as the previous value selected for that same widget. This could apply to reactive values derived from user input, where I want the old and the new value.
The problem is that if I try to save the value of a widget, then the variable containing that value has to be reactive or it will not update every time the widget changes. But, if I save the the value in a reactive context it will always give me the current value, not the previous one.
How can I save the previous value of a widget, but still have it update every time the user changes the widget?
Is there a way that does not require the use of an actionButton every time the user changes things? Avoiding an actionButton can be desirable with adding one is otherwise unnecessary and creates excess clicking for the user.
Seeing as the session flush event method seems to be broken for this purpose, here is an alternative way to do it using an observeEvent construct and a reactive variable.
library(shiny)
ui <- fluidPage(
h1("Memory"),
sidebarLayout(
sidebarPanel(
numericInput("val", "Next Value", 10)
),
mainPanel(
verbatimTextOutput("curval"),
verbatimTextOutput("lstval")
)
)
)
server <- function(input,output,session) {
rv <- reactiveValues(lstval=0,curval=0)
observeEvent(input$val, {rv$lstval <- rv$curval; rv$curval <- input$val})
curre <- reactive({req(input$val); input$val; rv$curval})
lstre <- reactive({req(input$val); input$val; rv$lstval})
output$curval <- renderPrint({sprintf("cur:%d",curre())})
output$lstval <- renderPrint({sprintf("lst:%d",lstre())})
}
options(shiny.reactlog = TRUE)
shinyApp(ui, server)
Yielding:
Update This answer was posted before the advent of the reactiveValues/observeEvent model in shiny. I think that #MikeWise 's answer is the better way to do this.
After some playing around this is what I came up with. The ui.r is nothing special
ui.r
library(shiny)
ui <- shinyUI(fluidPage(
sidebarLayout(
sidebarPanel(
selectizeInput(inputId="XX", label="Choose a letter",choices=letters[1:5])
),
mainPanel(
textOutput("Current"),
textOutput("old")
)
)
))
"Current" will display the current selection and "old" displays the previous selection.
In the server.r I made use of three key functions: reactiveValues, isolate and session$onFlush.
server.r
library(shiny)
server <- function(input, output,session) {
Values<-reactiveValues(old="Start")
session$onFlush(once=FALSE, function(){
isolate({ Values$old<-input$XX })
})
output$Current <- renderText({paste("Current:",input$XX)})
output$old <- renderText({ paste("Old:",Values$old) })
}
The server.r works like this.
First, Values$old is created using the reactiveValues function. I gave it the value "Start" to make it clear what was happening on load up.
Then I added a session$onFlush function. Note that I have session as an argument in my server function. This will run every time that shiny flushes the reactive system - such as when the selectizeInput is changed by the user. What is important is that it will run before input$XX gets a new value - so the value has changed at the selectizeInput but not at XX.
Inside the session$onFlush I then assign the outgoing value of XX to Values$old. This is done inside an isolate() as this will prevent any problems with input$XX gets updated with the new values. I can then use input$XX and Values$old in the renderText() functions.
I am new to Shiny and trying to build a more accessible input and output for a function I built. I am giving this to people that don't run R so trying to build something that runs my functions in the background and then spits out the answer.
I am having some trouble getting everything in the way that I want it unfortunately and dealing with a bunch of errors. However, here is my more pointed question:
The actual function that I want to run takes a name (in quotations as "Last,First") and a number.
PredH("Last,First",650)
So I want a shiny application that takes a name input and a number input that then runs this program and then spits back out a data table with my answer. So a couple of questions.
How do I get it in the right form to input into my equation on the server side script, do I need to return it in the function so it can be accessed using a function$table type access? (Right now I am just printing using cat() function in the console for the function but know that may not be usable for this type of application.
I want to return a dataframe that can be gotten at PredH14$table. How do I go about building that shiny?
Here is my code so far:
UI:
library(shiny)
shinyUI(pageWithSidebar(
# Application title
headerPanel("Miles Per Gallon"),
# Sidebar with controls to select the variable to plot against mpg
# and to specify whether outliers should be included
sidebarPanel(
textInput("playername", "Player Name (Last,First):", "Patch,Trevor"),
radioButtons("type", "Type:",
list("Pitcher" = "P",
"Hitter" = "H"
)),
numericInput("PAIP", "PA/IP:", 550),
submitButton("Run Comparables")
),
mainPanel(
textOutput("name")
)
Server:
library(shiny)
shinyServer(function(input, output) {
sliderValues <- reactive({
data.frame(
Name = c("name", "PA"),
Value = c(as.character(playername),
PAIP),
stringsAsFactors=FALSE)
})
name=input[1,2]
PAIP=input[2,2]
testing <- function(name,PAIP){
a=paste(name,PAIP)
return(a) }
output$name=renderText(testing$a)
})
I am not quite sure I understood your question 100% but I clearly see you are wondering how to pass the input of the UI into the server and maybe, the other way back.
In your server code, clearly you are not getting any input from the UI. Basically you have created three input variables in your ui.R:
1. input$playername
2. input$type
3. input$PAIP
And one output:
1. output$name
Just let you know, the function sliderValues <- reactive(..) is called every time there is any input from the input... like people click the dropdown list or people modifies words in the text box.
You can even get started without the submit button just to get started. But the existence of the submit button actually makes everything easier. Create a submit button for an input form. Forms that include a submit button do not automatically update their outputs when inputs change, rather they wait until the user explicitly clicks the submit button.
So you can put your code in a way similar like this:
# server.R
library(shiny)
shinyServer(function(input, output) {
sliderValues <- reactive({
result <- ... input$playername ... input$type ... input$PAIP
return(result)
})
output$name <- renderPlot/renderText (... sliderValues...)
})
# ui.R
library(shiny)
shinyUI(pageWithSidebar(
headerPanel("Miles Per Gallon"),
sidebarPanel(
textInput("playername" ... ),
radioButtons("type" ... ),
numericInput("PAIP" ... ),
submitButton("...")
),
mainPanel(
textOutput/plotOutput...("name")
)
))
In the end, check out the shiny example that might be what you want.
library(shiny)
runExample('07_widgets')