How to use selectInput outputs
The key thing to note about using the output (result / choice) from a selectInput control is that the output HAS to be returned in a shiny reactive control, e.g. renderText(), renderPlot(), observeEvent() etc.
The selectInput output (result / choice) is called with the format input$inputID.
E.g. if our selectInput ID is “choose”, the selection control output is called using input$choose.
The selectInput outputs below work because they are wrapped in reactive functions, and will update when the input selection changes:
####---- inputID = "choose"
renderText({input$choose})
####---- inputID = "n_breaks"
renderPlot({
hist(faithful$eruptions, probability = TRUE, breaks =
as.numeric(input$n_breaks),
xlab = "Duration (minutes)", main = "Geyser eruption duration") ...You can also create an output variable with renderText(), which you call elsewhere in the layout using textOutput():
# Create an output from the selectInput choice, named 'chosen2
output$chosen2 <- renderText({input$choose})
# Use textOutput to place the output 'chosen2' in your layout
textOutput("chosen2")TheselectInput output below doesn’t work because it’s called directly by a ‘static’ function, which will not update if the selectInput control is refreshed:
# This is not in a reactive context so won't work
chosen1 <- input$choose
## Error in .getReactiveEnvironment()$currentContext(): Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.)Example selectInput code – input and output
---
title: "Shiny SelectInput"
runtime: shiny
output: html_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
library(shiny)
```
```{r error=TRUE}
inputPanel(selectInput(inputID="choose",
label="Select", choices =c("Red","Green","Blue")),
renderText({paste0("You chose: ",input$choose)}))
# use a reactive context to display the selectInput choice
# if wanted, we can also include this within the inputPanel above
renderText({input$choose})
# This is not in a reactive context so won't work
chosen1 <- input$choose
# Create an output from the selectInput choice
output$chosen2 <- renderText({input$choose})
# Use textOutput to place the output in your layout
textOutput("chosen2")
# no input panel formatting
selectInput("choose2",label="Select", choices =c("Red","Green","Blue"))
# input panel formatting with inputPanel()
inputPanel(selectInput("choose", label="Select",choices
=c("Red","Green","Blue")))
```