I want to change the number of choices in selectInput(). The following reprex works if the new choices are equal in number to the original choices, but if additional (or fewer) choices are offered, the code does not work. How can I get shiny to accept not just new choices for selectInput(), but a new number of choices? Thanks in advance for any help.
Philip
library(shiny)
ui <- fluidPage(
tabPanel("tbls",
selectInput("tab1",label="Pick a table:",choices=c("a","b","c")),
selectInput("cht1",label="Pick a time series:",choices=c("d","e","f"))
)
)
server <- function(input,output,session) {
Nchoices <- reactive({case_when(
input$tab1=="a" ~c("d","e","f"),
input$tab1=="b" ~c("g","h","i"),
input$tab1=="c" ~c("j","k","l","m") # adding one more choice breaks the code
)})
observe({updateSelectInput(session,"cht1",
label="Pick a time series:",choices=Nchoices(),selected=NULL)})
observe(print(Nchoices()))
}
shinyApp(ui, server)
Instead of case_when, try to use switch. Also, renderUI might be useful. Try this
library(shiny)
ui <- fluidPage(
tabPanel("tbls",
selectInput("tab1",label="Pick a table:",choices=c("a","b","c")),
uiOutput("myselect")
#selectInput("cht1",label="Pick a time series:",choices=c("d","e","f"))
)
)
server <- function(input,output,session) {
Nchoices <- reactive({
switch(input$tab1,
"a" = c("d","e","f"),
"b" = c("g","h"),
"c" = c("j","k","l","m") # adding one more choice breaks the code
)
})
output$myselect <- renderUI({
req(input$tab1)
selectInput("cht1",label="Pick a time series:",choices=Nchoices())
})
observe(print(Nchoices()))
}
shinyApp(ui, server)
Please note that in case_when All RHS values need to be of the same type. Inconsistent types will throw an error.
Related
I am trying to change the choices in the second selectInput() based on the choice made in the first selectInput(). Here's is my reprex. Thanks in advance for any help.
library(shiny)
ui <- fluidPage(
tabPanel("tbls",
selectInput("tab1",label="Pick a table:",choices=c("a","b","c")),
selectInput("cht1",label="Pick a time series:",choices=c("d","e","f"))
)
)
server <- function(input,output,session) {
Nchoices <- reactive({case_when(
input$tab1=="a" ~c("d","e","f"),
input$tab1=="b" ~c("g","h","i"),
input$tab1=="c" ~c("j","k","l")
)})
observeEvent(input$tab1,{updateSelectInput(session,input$cht1,
label="Pick a time series:",choices=Nchoices(),selected=NULL)})
observe(print(Nchoices()))
}
shinyApp(ui, server)
In a shiny app (by RStudio), on the server side, I have a reactive that returns a list of variables by parsing the content of a textInput. The list of variables is then used in selectInput and/or updateSelectInput.
I can't make it work. Any suggestions?
I have made two attempts. The first approach is to use the reactive outVar directly into selectInput. The second approach is to use the reactive outVar in updateSelectInput. Neither works.
server.R
shinyServer(
function(input, output, session) {
outVar <- reactive({
vars <- all.vars(parse(text=input$inBody))
vars <- as.list(vars)
return(vars)
})
output$inBody <- renderUI({
textInput(inputId = "inBody", label = h4("Enter a function:"), value = "a+b+c")
})
output$inVar <- renderUI({ ## works but the choices are non-reactive
selectInput(inputId = "inVar", label = h4("Select variables:"), choices = list("a","b"))
})
observe({ ## doesn't work
choices <- outVar()
updateSelectInput(session = session, inputId = "inVar", choices = choices)
})
})
ui.R
shinyUI(
basicPage(
uiOutput("inBody"),
uiOutput("inVar")
)
)
A short while ago, I posted the same question at shiny-discuss, but it has generated little interest, so I'm asking again, with apologies, https://groups.google.com/forum/#!topic/shiny-discuss/e0MgmMskfWo
Edit 1
#Ramnath has kindly posted a solution that appears to work, denoted Edit 2 by him. But that solution does not address the problem because the textinput is on the ui side instead of on the server side as it is in my problem. If I move the textinput of Ramnath's second edit to the server side, the problem crops up again, namely: nothing shows and RStudio crashes. I found that wrapping input$text in as.character makes the problem disappear.
Edit 2
In further discussion, Ramnath has shown me that the problem arises when the server attempts to apply the dynamic function outVar before its arguments have been returned by textinput. The solution is to first check whether is.null(input$inBody) exists.
Checking for existence of arguments is a crucial aspect of building a shiny app, so why did I not think of it? Well, I did, but I must have done something wrong! Considering the amount of time I spent on the problem, it's a bitter experience. I show after the code how to check for existence.
Below is Ramnath's code with textinput moved to the server side. It crashes RStudio so don't try it at home. (I have used his notation)
library(shiny)
runApp(list(
ui = bootstrapPage(
uiOutput('textbox'), ## moving Ramnath's textinput to the server side
uiOutput('variables')
),
server = function(input, output){
outVar <- reactive({
vars <- all.vars(parse(text = input$text)) ## existence check needed here to prevent a crash
vars <- as.list(vars)
return(vars)
})
output$textbox = renderUI({
textInput("text", "Enter Formula", "a=b+c")
})
output$variables = renderUI({
selectInput('variables2', 'Variables', outVar())
})
}
))
The way I usually check for existence is like this:
if (is.null(input$text) || is.na(input$text)){
return()
} else {
vars <- all.vars(parse(text = input$text))
return(vars)
}
Ramnath's code is shorter:
if (!is.null(mytext)){
mytext = input$text
vars <- all.vars(parse(text = mytext))
return(vars)
}
Both seem to work, but I'll be doing it Ramnath's way from now on: maybe an unbalanced bracket in my construct had earlier prevented me to make the check work? Ramnath's check is more direct.
Lastly, I'd like to note a couple of things about my various attempts to debug.
In my debugging quest, I discovered that there is an option to "rank" the priority of "outputs" on the server side, which I explored in an attempt to solve my problem, but didn't work since the problem was elsewhere. Still, it's interesting to know and seems not very well known at this time:
outputOptions(output, "textbox", priority = 1)
outputOptions(output, "variables", priority = 2)
In that quest, I also tried try:
try(vars <- all.vars(parse(text = input$text)))
That was pretty close, but still did not fix it.
The first solution I stumbled upon was:
vars <- all.vars(parse(text = as.character(input$text)))
I suppose it would be interesting to know why it worked: is it because it slows things down enough? is it because as.character "waits" for input$text to be non-null?
Whatever the case may be, I am extremely grateful to Ramnath for his effort, patience and guidance.
You need to use renderUI on the server side for dynamic UIs. Here is a minimal example. Note that the second drop-down menu is reactive and adjusts to the dataset you choose in the first one. The code should be self-explanatory if you have dealt with shiny before.
runApp(list(
ui = bootstrapPage(
selectInput('dataset', 'Choose Dataset', c('mtcars', 'iris')),
uiOutput('columns')
),
server = function(input, output){
output$columns = renderUI({
mydata = get(input$dataset)
selectInput('columns2', 'Columns', names(mydata))
})
}
))
EDIT. Another Solution using updateSelectInput
runApp(list(
ui = bootstrapPage(
selectInput('dataset', 'Choose Dataset', c('mtcars', 'iris')),
selectInput('columns', 'Columns', "")
),
server = function(input, output, session){
outVar = reactive({
mydata = get(input$dataset)
names(mydata)
})
observe({
updateSelectInput(session, "columns",
choices = outVar()
)})
}
))
EDIT2: Modified Example using parse. In this app, the text formula entered is used to dynamically populate the dropdown menu below with the list of variables.
library(shiny)
runApp(list(
ui = bootstrapPage(
textInput("text", "Enter Formula", "a=b+c"),
uiOutput('variables')
),
server = function(input, output){
outVar <- reactive({
vars <- all.vars(parse(text = input$text))
vars <- as.list(vars)
return(vars)
})
output$variables = renderUI({
selectInput('variables2', 'Variables', outVar())
})
}
))
As far as I can tell, the problem is that input$inBody does not retrieve a character even though the selectInput function is given a character as value, namely value = "a+b+c". The solution is therefore to wrap input$inBody in a as.character
The following works:
The observe approach with updateSelectInput:
observe({
input$inBody
vars <- all.vars(parse(text=as.character(input$inBody)))
vars <- as.list(vars)
updateSelectInput(session = session, inputId = "inVar", choices = vars)
})
The reactive approach with selectInput:
outVar <- reactive({
vars <- all.vars(parse(text=as.character(input$inBody)))
vars <- as.list(vars)
return(vars)
})
output$inVar2 <- renderUI({
selectInput(inputId = "inVar2", label = h4("Select:"), choices = outVar())
})
Edit: I have edited my question with an explanation based on Ramnath's feedback. Ramnath has explained the problem and provided a better solution, which I give as an edit of my question. I'll keep this answer for the record.
server.R
### This will create the dynamic dropdown list ###
output$carControls <- renderUI({
selectInput("cars", "Choose cars", rownames(mtcars))
})
## End dynamic drop down list ###
## Display selected results ##
txt <- reactive({ input$cars })
output$selectedText <- renderText({ paste("you selected: ", txt() ,sep="") })
## End Display selected results ##
ui.R
uiOutput("carControls"),
br(),
textOutput("selectedText")
I want a local variable in each session that can be updated by an input, which can be used by all other functions in the server. See the simple example below, I want the object to be updated when the user changes value but it doesn't?
library(shiny)
# Define UI for application
ui = shinyUI(pageWithSidebar(
# Application title
headerPanel("Hello Shiny!"),
# Sidebar with a slider input for data type
sidebarPanel(
selectInput("data",
"Pick letter to us in complex app?", choices = c("A","B"),
selected = "A")
),
# Print letter
mainPanel(
textOutput("Print")
)
))
server =shinyServer(function(input, output) {
MYLetter = "A";
updateData = reactive({
if (input$data == "A") {
MYLetter <<- "A"
} else {
MYLetter <<- "B"
}
})
output$Print <- renderText({
print(MYLetter)
})
})
shinyApp(ui, server)
I feel a solution will be global variables, but if two people are on the app at the same time. Will one person assigning a new value to a global variable change the variable for the other user?
There's a couple problems with your code. Here is the code that you want, I tried making very minimal changes to your code in order to make it work:
ui = shinyUI(pageWithSidebar(
# Application title
headerPanel("Hello Shiny!"),
# Sidebar with a slider input for data type
sidebarPanel(
selectInput("data",
"Pick letter to us in complex app?", choices = c("A","B"),
selected = "A")
),
# Print letter
mainPanel(
textOutput("Print")
)
))
server =shinyServer(function(input, output) {
MYLetter = reactiveVal("A");
observe({
if (input$data == "A") {
MYLetter("A")
} else {
MYLetter("B")
}
})
output$Print <- renderText({
print(MYLetter())
})
})
shinyApp(ui, server)
Essentially the two problems were:
What you are looking for is creating a reactive value with reactiveVal() or reactiveValues(). You're absolutely correct that creating a global variable is not the correct solution, because then it would be shared among all the users. It also is not reactive that way.
I changed the reactive({...}) to an observe({...}). It's very important to understand the difference between a reactive and an observer. I suggest reading online about it. I changed it to an observe because you weren't returning a value that was being used - rather, you were making an assignment within it.
I am trying to create numeric boxes for all column names in a data set. I have written below code but this displays a blank page. Not sure what the error is. Any suggestions?
library(shiny)
library(readr)
shinyApp(
ui <- fluidPage(
uiOutput("TestColumns")
),
server <- function(input, output) {
data_set <- read.csv("Data/170210_Flat_File.csv")
output$TestColumns <- renderUI({
for(i in names(data_set)){
numericInput(i, i,30)
}}
)})
First off, when you ask questions you should ALWAYS post a minimal reproducible example. That is basically something that we can run to replicate the issue you are having so that it is much easier for us to help you. This way we don't have to go about using different data, trying to figure out exactly what your error is. See this link for a good intro: How to make a great R reproducible example?
Next to your question - since you didn't explicitly post an error you were seeing or explicitly state what your issue was I'm going to go ahead and assume that your issue is that you don't see any UI's popping up when you run your Shiny App (this is what I got when I tried running your code with different sample data).
The reason you aren't seeing anything is because you aren't returning any objects from your for loop. If you really wanted to do a for loop you would have to loop through, store everything in a list, then return that list. Note that I had to use R's built in data because you didn't provide any. Something like this would work:
shinyApp(
ui <- fluidPage(
#numericInput("test","test",30),
uiOutput("TestColumns")
),
server <- function(input, output) {
data_set <- mtcars
output$TestColumns <- renderUI({
L<-vector("list",length(names(data_set)))
for(i in names(data_set)){
L[[i]]<-numericInput(i, i,30)
}
return(L)
})})
This should give you your desired result. However, the above is unnecessarily complicated. I suggest you use an lapply instead. Something like this is much better in my opinion:
shinyApp(
ui <- fluidPage(
#numericInput("test","test",30),
uiOutput("TestColumns")
),
server <- function(input, output) {
data_set <- mtcars
output$TestColumns <- renderUI({
lapply(names(data_set),function(x){numericInput(x,x,30)})
})})
ui <- bootstrapPage(
fluidRow(
column(4,offset = 2,
tags$h4("numeric inputs"),
uiOutput('mtcars_numerics') # These will be all the numeric inputs for mtcars
),
column(6,
tags$h4("current input values"),
verbatimTextOutput('show_vals') # This will show the current value and id of the inputs
)
)
)
server <- function(input, output, session){
# creates the output UI elements in the loop
output$mtcars_numerics <- renderUI({
tagList(lapply(colnames(mtcars), function(i){ # must use `tagList` `
column(3,
numericInput(
inputId = sprintf("mt_col_%s",i), # Set the id to the column name
label = toupper(i), # Label is upper case of the col name
min = min(mtcars[[i]]), # min value is the minimum of the column
max = max(mtcars[[i]]), # max is the max of the column
value = mtcars[[i]][[1]] # first value set to the first row of the column
))
})
)
})
# So we can see the values and ids in the ui for testing
output$show_vals <- renderPrint({
all_inputs <- names(session$input)
input_vals <- plyr::ldply(all_inputs, function(i){
data.frame(input_name = i, input_value = input[[i]],stringsAsFactors = FALSE)
})
input_vals
})
}
shinyApp(ui, server)
Results in:
In a shiny app (by RStudio), on the server side, I have a reactive that returns a list of variables by parsing the content of a textInput. The list of variables is then used in selectInput and/or updateSelectInput.
I can't make it work. Any suggestions?
I have made two attempts. The first approach is to use the reactive outVar directly into selectInput. The second approach is to use the reactive outVar in updateSelectInput. Neither works.
server.R
shinyServer(
function(input, output, session) {
outVar <- reactive({
vars <- all.vars(parse(text=input$inBody))
vars <- as.list(vars)
return(vars)
})
output$inBody <- renderUI({
textInput(inputId = "inBody", label = h4("Enter a function:"), value = "a+b+c")
})
output$inVar <- renderUI({ ## works but the choices are non-reactive
selectInput(inputId = "inVar", label = h4("Select variables:"), choices = list("a","b"))
})
observe({ ## doesn't work
choices <- outVar()
updateSelectInput(session = session, inputId = "inVar", choices = choices)
})
})
ui.R
shinyUI(
basicPage(
uiOutput("inBody"),
uiOutput("inVar")
)
)
A short while ago, I posted the same question at shiny-discuss, but it has generated little interest, so I'm asking again, with apologies, https://groups.google.com/forum/#!topic/shiny-discuss/e0MgmMskfWo
Edit 1
#Ramnath has kindly posted a solution that appears to work, denoted Edit 2 by him. But that solution does not address the problem because the textinput is on the ui side instead of on the server side as it is in my problem. If I move the textinput of Ramnath's second edit to the server side, the problem crops up again, namely: nothing shows and RStudio crashes. I found that wrapping input$text in as.character makes the problem disappear.
Edit 2
In further discussion, Ramnath has shown me that the problem arises when the server attempts to apply the dynamic function outVar before its arguments have been returned by textinput. The solution is to first check whether is.null(input$inBody) exists.
Checking for existence of arguments is a crucial aspect of building a shiny app, so why did I not think of it? Well, I did, but I must have done something wrong! Considering the amount of time I spent on the problem, it's a bitter experience. I show after the code how to check for existence.
Below is Ramnath's code with textinput moved to the server side. It crashes RStudio so don't try it at home. (I have used his notation)
library(shiny)
runApp(list(
ui = bootstrapPage(
uiOutput('textbox'), ## moving Ramnath's textinput to the server side
uiOutput('variables')
),
server = function(input, output){
outVar <- reactive({
vars <- all.vars(parse(text = input$text)) ## existence check needed here to prevent a crash
vars <- as.list(vars)
return(vars)
})
output$textbox = renderUI({
textInput("text", "Enter Formula", "a=b+c")
})
output$variables = renderUI({
selectInput('variables2', 'Variables', outVar())
})
}
))
The way I usually check for existence is like this:
if (is.null(input$text) || is.na(input$text)){
return()
} else {
vars <- all.vars(parse(text = input$text))
return(vars)
}
Ramnath's code is shorter:
if (!is.null(mytext)){
mytext = input$text
vars <- all.vars(parse(text = mytext))
return(vars)
}
Both seem to work, but I'll be doing it Ramnath's way from now on: maybe an unbalanced bracket in my construct had earlier prevented me to make the check work? Ramnath's check is more direct.
Lastly, I'd like to note a couple of things about my various attempts to debug.
In my debugging quest, I discovered that there is an option to "rank" the priority of "outputs" on the server side, which I explored in an attempt to solve my problem, but didn't work since the problem was elsewhere. Still, it's interesting to know and seems not very well known at this time:
outputOptions(output, "textbox", priority = 1)
outputOptions(output, "variables", priority = 2)
In that quest, I also tried try:
try(vars <- all.vars(parse(text = input$text)))
That was pretty close, but still did not fix it.
The first solution I stumbled upon was:
vars <- all.vars(parse(text = as.character(input$text)))
I suppose it would be interesting to know why it worked: is it because it slows things down enough? is it because as.character "waits" for input$text to be non-null?
Whatever the case may be, I am extremely grateful to Ramnath for his effort, patience and guidance.
You need to use renderUI on the server side for dynamic UIs. Here is a minimal example. Note that the second drop-down menu is reactive and adjusts to the dataset you choose in the first one. The code should be self-explanatory if you have dealt with shiny before.
runApp(list(
ui = bootstrapPage(
selectInput('dataset', 'Choose Dataset', c('mtcars', 'iris')),
uiOutput('columns')
),
server = function(input, output){
output$columns = renderUI({
mydata = get(input$dataset)
selectInput('columns2', 'Columns', names(mydata))
})
}
))
EDIT. Another Solution using updateSelectInput
runApp(list(
ui = bootstrapPage(
selectInput('dataset', 'Choose Dataset', c('mtcars', 'iris')),
selectInput('columns', 'Columns', "")
),
server = function(input, output, session){
outVar = reactive({
mydata = get(input$dataset)
names(mydata)
})
observe({
updateSelectInput(session, "columns",
choices = outVar()
)})
}
))
EDIT2: Modified Example using parse. In this app, the text formula entered is used to dynamically populate the dropdown menu below with the list of variables.
library(shiny)
runApp(list(
ui = bootstrapPage(
textInput("text", "Enter Formula", "a=b+c"),
uiOutput('variables')
),
server = function(input, output){
outVar <- reactive({
vars <- all.vars(parse(text = input$text))
vars <- as.list(vars)
return(vars)
})
output$variables = renderUI({
selectInput('variables2', 'Variables', outVar())
})
}
))
As far as I can tell, the problem is that input$inBody does not retrieve a character even though the selectInput function is given a character as value, namely value = "a+b+c". The solution is therefore to wrap input$inBody in a as.character
The following works:
The observe approach with updateSelectInput:
observe({
input$inBody
vars <- all.vars(parse(text=as.character(input$inBody)))
vars <- as.list(vars)
updateSelectInput(session = session, inputId = "inVar", choices = vars)
})
The reactive approach with selectInput:
outVar <- reactive({
vars <- all.vars(parse(text=as.character(input$inBody)))
vars <- as.list(vars)
return(vars)
})
output$inVar2 <- renderUI({
selectInput(inputId = "inVar2", label = h4("Select:"), choices = outVar())
})
Edit: I have edited my question with an explanation based on Ramnath's feedback. Ramnath has explained the problem and provided a better solution, which I give as an edit of my question. I'll keep this answer for the record.
server.R
### This will create the dynamic dropdown list ###
output$carControls <- renderUI({
selectInput("cars", "Choose cars", rownames(mtcars))
})
## End dynamic drop down list ###
## Display selected results ##
txt <- reactive({ input$cars })
output$selectedText <- renderText({ paste("you selected: ", txt() ,sep="") })
## End Display selected results ##
ui.R
uiOutput("carControls"),
br(),
textOutput("selectedText")