r - Rmarkdown and Shiny input

Question

I'm attempting my first Markdown doc and everything has been going smoothly until I get the error

 "Error in eval(expr, envir, enclos) : object 'input' not found"

with this chunk

{r, echo=FALSE}

inputPanel(
radioButtons("category",label= "Select  Category",choices=c("diffPts","diffGF","diffGA","diffGD","diffpos"),inline = TRUE)
)
   renderPlot({
   ggplot(clubSeason, aes(x=team, y=input$category)) + geom_boxplot()
})

if I hardcode e.g y="diffPts" the chart displays. Putting a print() around the ggplot does not help

TIA

Answer 1

Following runs fine for me. The value of ìnput$category` is printied as expected

---
title: "Untitled"
runtime: shiny
output: html_document
---

```{r, echo=FALSE}
library(ggplot2)
inputPanel(
   radioButtons("category",label= "Select  Category",choices=c("diffPts","diffGF","diffGA","diffGD","diffpos"),inline = TRUE)
)
renderPlot({
   print(input$category)
   ggplot(faithful, aes(x=eruptions, y=waiting)) + geom_boxplot()
})
```

UPDATE:

The issue appears to be with the aes function being passed a string. You can use aes_string instead:

renderPlot({
   ggplot(clubSeason, aes_string(x='team', y=input$category)) + geom_boxplot()
})