I am new to shiny, I have been stuck on this for quite a while and the things I tried and read so far held no fruits. I have a dropdown, where the user will choose a Question, then depending on the question, a drop down will be populated with the response numbers. After the user chooses the response number a map will be plotted. I have gone through the dynamic drop down list, that is done. But I cannot get access to the second user input, the response number, so I can select my data for the map accordingly. I feel like this is really simple I don't know why this does not work. I am getting this error:
Error in .getReactiveEnvironment()$currentContext() : Operation not
allowed without an active reactive context. (You tried to do something
that can only be done from inside a reactive expression or observer.)
My code is as follows, I have tentatively put in special cases and later I will expand to a general case with lists.
library(shiny)
runApp(list(
ui = shinyUI(pageWithSidebar(
headerPanel('Dialect Comparison'),
sidebarPanel(
selectInput('Question', 'Choose The Question', c('100. Do you cut or mow the lawn or grass?'='Q100',
'101. Do you pass in homework or hand in homework?'='Q101')),
uiOutput('C')
),
mainPanel(
plotOutput('plot')
)
)
),
server = function(input, output){
output$C = renderUI({
ques = input$Question
selectInput('Choice', 'Choose The Response', seq(0,max(ling_data[,ques])))
})
##########
#The Data#
##########
#text = renderPrint({'uhu'})
#print(text()) #THIS WORKS
choice_number = renderPrint({input$Choice}) #http://shiny.rstudio.com/gallery/dynamic-ui.html
print(choice_number()) #it fails here
...
})
}
))
Reactive variables, including inputs, can be accessed only in a reactive scope created using one of the following:
shiny::reactive, shiny::eventReactive
shiny::observe, shiny::observeEvent
shiny::render*
or inside shiny::isolate block.
For actions like logging you probably want observe block:
observe({print(choice_number())})
Related
I have a shiny app that I am building where the user selects a report from a radio button menu, and then the table displays on the page. I would like to add an option for the user to simultaneously view all reports. I have found something close to what I want from this thread https://gist.github.com/wch/5436415/ , but I can't quite seem to implement it properly. Basically, I think what I have to do is:
In the UI, make a call to uiOutput() to reactively update the User Interface. I will need multiple calls to htmlOutput() if the user selects the "all" button, but only one call to htmlOutput() if the use simply selects one report. For the record, I am creating my tables with the kable() function, which is why I call htmlOutput() instead of tableOutput().
In the server function, I need to make a call to renderUI() that provides the instructions on how many htmlOutput() calls there will be and which reports will be in each call.
Create a loop that then makes a call to renderText that then sends the html code for the htmlOutput function to interpret.
I can get most of the way there. I can get Shiny to have reactive tables, and output individual reports, but I am struggling to get the looping range to reactively update so that I see all three tables in my testing app. Here is what I have:
library(shiny)
library(shinydashboard)
library(knitr)
library(kableExtra)
data("cars")
data("iris")
data("airquality")
UI<-dashboardPage(
dashboardHeader(),
dashboardSidebar(sidebarMenu(
menuItem("Options", radioButtons(inputId = "Tables", label="test", choices= c("cars", "iris", "airquality", "all"))
) )),
dashboardBody(
uiOutput(outputId = "TABLE"),
textOutput("N")
)
)
server<-function(input, output){
TBL<-list("cars", "iris", "airquality")
T1<-knitr::kable(head(cars))
T2<-knitr::kable(head(iris))
T3<-knitr::kable(head(airquality))
tmp<-list(cars=T1, iris=T2, airquality=T3)
TABLES<-reactive({
ifelse(input$Tables=="all", tmp, tmp[input$Tables])
})
val<-reactive({
tmp<-TABLES()
length(tmp)})
n<-isolate(val())
output$TABLE<-renderUI({
req(input$Tables)
TAB<-TABLES()
TBL<-names(TAB)
tbls<-lapply(1:length(TBL), function(i){
tblnm<-paste("tbl", i, sep="_")
htmlOutput(tblnm)})
do.call(tagList, tbls)
})#Close Render UI
for(i in 1:n){
local({
j<-i
tblnm<-paste("tbl", j, sep="_")
output[[tblnm]]<-renderText(kables(TABLES()))
})
}
output$N<-renderText(n)
}#Close Server
shinyApp(ui = UI, server = server)
Here is where I think I am going wrong:
I included a textOutput() for the value of n, and despite having the reactive() call to get the length of TABLES, when I isolate() I still get the value of 1 even when I select the "all" report button, which should give me 3. Am I misinterpreting how isolate() works? Is there another way to get a value out of a reactive() function that can be used outside of a *Output() or reactive() function? Any guidance would be much appreciated. Thanks so much.
I think your server function is needlessly complex.
render functions are a reactive context themselves, so no need to define variables which only exist in those contexts as specifically reactive.
server<-function(input, output){
TBL<-list("cars", "iris", "airquality")
T1<-knitr::kable(head(cars))
T2<-knitr::kable(head(iris))
T3<-knitr::kable(head(airquality))
tmp<-list(cars=T1, iris=T2, airquality=T3)
output$TABLE<-renderUI({
if(input$Tables=="all"){ind <- names(tmp)}else{ind <- input$Tables}
lapply(tmp, HTML)[ind]
})
output$N <- renderText({
if(input$Tables=="all"){ind <- names(tmp)}else{ind <- input$Tables}
length(ind)
})
}
I want to use some information of a selectInput in a renderUi, e.g. the length of selected items (renderUi depends on this number).
Unfortunately I haven't find a solution yet. Below a short simplified example, which should display the length of selected items. I guess there is a problem either with the return type of input or with the encoding of I/O.
Please note: I tried already renderPrint, which is working! But I need the information about the length of selectInput within a renderUi, since I want to create further ui elements based on the selected number.
Ui.R:
library(shiny)
shinyUI(fluidPage(
selectInput("first","first",choices=c("a","b"),multiple=TRUE),
uiOutput("hallo")
))
Server.R:
library(shiny)
shinyServer(function(input, output) {
output$hallo <- renderUI({
print(length(input$first))
})
})
My goal is to have a tabsetPanel wrapped in a conditionalPanel whose condition is a global variable being false.
ui.R
mainPanel(
conditionalPanel("searchPage == \"false\"",
tabsetPanel(
tabPanel("Summary",htmlOutput("summary")),
tabPanel("Description", htmlOutput("description"))
))),
global.R
searchPage <- "true"
then in server.R I assign new values to it a few different times, but all like this:
observeEvent(input$openButton,
output$results <- renderUI({
textOutput("")
searchPage <- "false"
}))
No matter what I do, I always get "Uncaught ReferenceError: searchPage is not defined". I've tried changing the global.R to multiple different combinations of using quotes, not using quotes, using <- or <<-, making it this.searchPage, my.searchPage and numerous other things (of course always making server.R and ui.R match too), but haven't had much luck at all.
As mentioned in a comment on the question's post, this is a perfect usecase for the shinyjs toggle()/show()/hide() functions. Whenever you need to conditionally show something where the condition is not a simple javascript expression of an input, it's easy to use these functions instead of a conditionalPanel().
In order to use these functions, you need to have some way to specify the element you want to hide/show (in this case, the mainPanel()). The easist way to do this is to just wrap the entire panel in a div with an id. So define the panel like mainPanel(div(id = "mainpanel", ...)) and voila, there's an id to your panel, and now you can call shinyjs::show("mainpanel") or hide() whenever you want in the server code.
What you are trying to do is not really possible the way you are trying to do it (the server and client are in different environments and don't share variables). You will need to explicitly pass the value from server to client, and there are different approaches to doing that. One way:
library(shiny)
runApp(list(ui = fluidPage(
conditionalPanel(condition='output.bool',
HTML("Hello world")),
actionButton("btn","Press me to toggle")
),
server = function(input, output, session) {
value=TRUE
output$bool <- eventReactive(input$btn,{
value
})
outputOptions(output,"bool",suspendWhenHidden=FALSE)
observeEvent(input$btn,
value <<- !value
)
}))
There are probably better approaches. Hope this helps
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')