Conditional reactive logic shiny based flexdashboard - r

Question

I am trying to contiditonally do either one type of render (renderPlot) or another (renderText) based on some input. Here's what I tried:
---
title: "Citation Extraction"
output:
flexdashboard::flex_dashboard:
vertical_layout: scroll
orientation: rows
social: menu
source_code: embed
runtime: shiny
---
```{r setup, include=FALSE}
library(flexdashboard)
library(shiny)
```
Sidebar {.sidebar}
=====================================
```{r}
textInput("txt", "What's up?:")
```
Page 1
=====================================
### Chart A
```{r}
urtxt <- reactive({input$txt})
if (nchar(urtxt()) > 20){
renderPlot({plot(1:10, 1:10)})
} else {
renderPrint({
urtxt()
})
}
```
But it states:
So I tried adding a reactive around the conditional resulting in returning the function reactive returns.
reactive({
if (nchar(urtxt()) > 20){
renderPlot({plot(1:10, 1:10)})
} else {
renderPrint({
urtxt()
})
}
})
How can I have conditional reactive logic?

Answer 1

To get different kind of output depending on the length of the inputed character string you can do following:
1) Create a dynamic output uiOutput,
2) In the reactive environment renderUI, depending on the input, choose kind of the output.
3) Render the output
---
title: "Citation Extraction"
output:
flexdashboard::flex_dashboard:
vertical_layout: scroll
orientation: rows
social: menu
source_code: embed
runtime: shiny
---
```{r setup, include=FALSE}
library(flexdashboard)
library(shiny)
```
Sidebar {.sidebar}
=====================================
```{r, echo = F}
textInput("txt", "What's up?:", value = "")
```
Page 1
=====================================
### Chart A
```{r, echo = F}
uiOutput("dynamic")
output$dynamic <- renderUI({
if (nchar(input$txt) > 20) plotOutput("plot")
else textOutput("text")
})
output$plot <- renderPlot({ plot(1:10, 1:10) })
output$text <- renderText({ input$txt })
```