R help - Jul 2020 - brms does not work with R4.0.2

Hello,

I upgraded today to R4.0.2 from 3.6.3 on my Windows machine (actually
2 of them - first desktop and then laptop just to verify the problem)
and on both of them I am getting the following error when running the
brms::brm function example code.

```
> bprior1 <- prior(student_t(5,0,10), class = b) +
+     prior(cauchy(0,2), class = sd)
> fit1 <- brm(count ~ zAge + zBase * Trt + (1|patient),
+             data = epilepsy, family = poisson(), prior = bprior1)
Compiling the C++ model
>
> fit1
Error: object 'fit1' not found
```

I tried to get some more information by setting `silent = FALSE` but
nothing is being printed.
All I see is:

```
> brm(count ~ zAge + zBase * Trt + (1|patient),
+     data = epilepsy, family = poisson(), prior = bprior1, silent=FALSE)
Compiling the C++ model
>
```

R tools is installed and I did test that they work properly.
Also:

```
system.file(package = "StanHeaders")
[1] "C:/Users/wewol/OneDrive/Documents/R/win-library/4.0/StanHeaders"
```

Help highly appreciated.

Witek
--
Witold Eryk Wolski

Hello,

Got the following info from the brms package Maintainer.

"This is a caused by a problem in the current rstan CRAN version on
Windows and is not related to brms. You can find various threads that
deal with that topic on https://discourse.mc-stan.org/. For now, it
may be easiest to revert to rstan 2.19.3."

Thanks
Witek



On Mon, 13 Jul 2020 at 15:41, Witold E Wolski <wewolski at gmail.com>
wrote:
>
> Hello,
>
> I upgraded today to R4.0.2 from 3.6.3 on my Windows machine (actually
> 2 of them - first desktop and then laptop just to verify the problem)
> and on both of them I am getting the following error when running the
> brms::brm function example code.
>
> ```
> > bprior1 <- prior(student_t(5,0,10), class = b) +
> +     prior(cauchy(0,2), class = sd)
> > fit1 <- brm(count ~ zAge + zBase * Trt + (1|patient),
> +             data = epilepsy, family = poisson(), prior = bprior1)
> Compiling the C++ model
> >
> > fit1
> Error: object 'fit1' not found
> ```
>
> I tried to get some more information by setting `silent = FALSE` but
> nothing is being printed.
> All I see is:
>
> ```
> > brm(count ~ zAge + zBase * Trt + (1|patient),
> +     data = epilepsy, family = poisson(), prior = bprior1, silent=FALSE)
> Compiling the C++ model
> >
> ```
>
> R tools is installed and I did test that they work properly.
> Also:
>
> ```
> system.file(package = "StanHeaders")
> [1]
"C:/Users/wewol/OneDrive/Documents/R/win-library/4.0/StanHeaders"
> ```
>
> Help highly appreciated.
>
> Witek
> --
> Witold Eryk Wolski


-- 
Witold Eryk Wolski