Running on CentOS 7 with R 4.1.2 with fully-updated packages on 2022 March 17
produced the following error
```
   --- re-building ‘faustPFDA.Rmd’ using rmarkdown
   Quitting from lines 426-439 (faustPFDA.Rmd) 
   Error: processing vignette 'faustPFDA.Rmd' failed with diagnostics:
   Downdated VtV is not positive definite
   --- failed re-building ‘faustPFDA.Rmd’
``` 

when building vignettes on install, which blocked
the install. To allow the Rmd to complete even with the error (and allow at least to see part of that vignette and the other two vignettes
when installing with vignettes), I added
`error = TRUE` as an argument to `knitr::opts_chunk$set`.

In R3.6.3, using vectors with length greater than one in the condition of an if statement merely warned and used the first element, but past verion 4.something it throws an error. 

It's not entirely clear to me whether any or all would be better. Presumably any, as if there are any NAs then we would want to fix the behaviour. So that's what we went with.