Accessing objects outside of renderPlot()

[csarven]

Unless I'm doing something wrong, I can't seem to use objects defined outside of renderPlot(). For example, the following works:

library(shiny)
library(datasets)
library(ggplot2)

shinyServer(function(input, output) {
  output$plot <- renderPlot({
    g <- ggplot(mtcars, aes(mtcars[1][,], mtcars[2][,])) + geom_bar(stat="identity")
    print(g)
  })
})

However, the following does not:

library(shiny)
library(datasets)
library(ggplot2)

mpgData <- mtcars

shinyServer(function(input, output) {
  output$plot <- renderPlot({
    g <- ggplot(mpgData, aes(mpgData[1][,], mpgData[2][,])) + geom_bar(stat="identity")
    print(g)
  })
})

Gives "Error: object 'mpgData' not found"

[wch]

This is probably due to a bug in ggplot2. See tidyverse/ggplot2#743 If this is the source of the problem, the workaround is to pass environment = environment() to ggplot().

As a general note, it's better to name the columns of the data frame when you use aes(), instead of pulling out columns as you've done. Something like this:

  ggplot(mpgData, aes(x=mpg, y=cyl)) + geom_bar(stat="identity")

I believe that doing things this way will also avoid the ggplot2 bug.

[csarven]

Thanks for the notice: environment = environment() resolved the issue!

I agree that it is better to name x,y values, I only simplified for the example here. Naming them doesn't resolve the issue however, environment = environment() is the only way I can see it working at the moment.