req() error using the "select repetitive options" script in R Shiny courtesy of Mike Badescu

Hi all,
I wondering if anyone can urgently provide me with a solution to my problem.
I am using Mike Badescus script/work-around to enable selecting repetitive options" when selecting inputs in R shiny. The script is descrbed in the following link/thread:

I get the following error when trying to implement it:
Error in seq.default: 'to' must be of length 1

Below is the Backtrace I believe in reverse order):
1: execCallbacks(timeoutSecs, all, loop$id)
2: run_now(timeoutMs/1000, all = FALSE)
3: service(timeout)
4: serviceApp()
5: ..stacktracefloor..(serviceApp())
6: withCallingHandlers(expr, error = doCaptureStack)
7: domain$wrapSync(expr)
8: promises::with_promise_domain(createStackTracePromiseDomain(),
9: captureStackTraces({
10: ..stacktraceoff..(captureStackTraces({
11: runApp()

The error occurs when I choose a value more than once, if i choose different values there are no issues. I am implementing the script very straight forward in a function that sources a script in a separate file.
NOTE: If I run the function outside of R shiny, choosing repetitive values works fine, so I know that everything except R shiny works fine. I am also using the latest versions of both R shiny v 1.6.0 and R-4.1.1

I would appreciate if someone urgently provided me with a solution, thanks in advance


I was able to run the old script w/o any problem - this is puzzling. I copied my old scrip as is to a new file called app.R and pressed Run App

I am on Windows 10, with a fresh install of R 4.1.1, Shiny 1.6.0, RStudio 1.4.1717. I can select multiple "No"s and "Yes"es, regardless of whether the app is running in RStudio or in a browser (Chrome). There was no error, only the extra logging messages due to cat()

Maybe I am missing something - are there any additional steps you attempted? If so, could you please describe them one a time?

My gut feeling is that there is something not exactly right with your installation of R. At this point, I recommend:

  • restarting the computer (it happened to me too many times)
  • reinstalling R and RStudio, and shiny
    • make sure that you delete the old library first
    • the goal is to
  • try to install and run it on a different machine

Can you run the script "as is" in a new file?
Are there any other packages you are using that might overwrite some of the functions used in the script?