Running examples in 'rstanemax-Ex.R' failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: stan_emax
> ### Title: Bayesian Emax model fit with Stan
> ### Aliases: stan_emax
> 
> ### ** Examples
> 
> data(exposure.response.sample)
> fit1 <- stan_emax(response ~ exposure, data = exposure.response.sample,
+                   # the next line is only to make the example go fast enough
+                   chains = 1, iter = 500, seed = 12345)

SAMPLING FOR MODEL 'emax' NOW (CHAIN 1).
Chain 1: 
Chain 1: Gradient evaluation took 5.7e-05 seconds
Chain 1: 1000 transitions using 10 leapfrog steps per transition would take 0.57 seconds.
Chain 1: Adjust your expectations accordingly!
Chain 1: 
Chain 1: 
Chain 1: Iteration:   1 / 500 [  0%]  (Warmup)
Chain 1: Iteration:  50 / 500 [ 10%]  (Warmup)
Chain 1: Iteration: 100 / 500 [ 20%]  (Warmup)
Chain 1: Iteration: 150 / 500 [ 30%]  (Warmup)
Chain 1: Iteration: 200 / 500 [ 40%]  (Warmup)
Chain 1: Iteration: 250 / 500 [ 50%]  (Warmup)
Chain 1: Iteration: 251 / 500 [ 50%]  (Sampling)
Chain 1: Iteration: 300 / 500 [ 60%]  (Sampling)
Chain 1: Iteration: 350 / 500 [ 70%]  (Sampling)
Chain 1: Iteration: 400 / 500 [ 80%]  (Sampling)
Chain 1: Iteration: 450 / 500 [ 90%]  (Sampling)
Chain 1: Iteration: 500 / 500 [100%]  (Sampling)
Chain 1: 
Chain 1:  Elapsed Time: 0.272647 seconds (Warm-up)
Chain 1:                0.103063 seconds (Sampling)
Chain 1:                0.37571 seconds (Total)
Chain 1: 
Warning: The largest R-hat is NA, indicating chains have not mixed.
Running the chains for more iterations may help. See
http://mc-stan.org/misc/warnings.html#r-hat
Warning: Bulk Effective Samples Size (ESS) is too low, indicating posterior means and medians may be unreliable.
Running the chains for more iterations may help. See
http://mc-stan.org/misc/warnings.html#bulk-ess
Warning: Tail Effective Samples Size (ESS) is too low, indicating posterior variances and tail quantiles may be unreliable.
Running the chains for more iterations may help. See
http://mc-stan.org/misc/warnings.html#tail-ess
> print(fit1)
Error in bquote(on.exit({ : 'where' must be an environment
Calls: print ... <Anonymous> -> <Anonymous> -> eval_bare -> exit_handler -> bquote
Execution halted