Error(s) in re-building vignettes:
  ...
--- re-building ‘FixedParameters.Rmd’ using rmarkdown
--- finished re-building ‘FixedParameters.Rmd’

--- re-building ‘nlsr-derivs.Rmd’ using rmarkdown
Loading required package: Ryacas

Attaching package: 'Ryacas'

The following object is masked from 'package:stats':

    integrate

The following objects are masked from 'package:base':

    %*%, diag, diag<-, lower.tri, upper.tri

! Undefined control sequence.
l.166 deriv.default(firstd, "x") : \n
                                       invalid expression in 

Error: processing vignette ‘nlsr-derivs.Rmd’ failed with diagnostics:
LaTeX failed to compile /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/nlsr.Rcheck/vign_test/nlsr/vignettes/nlsr-derivs.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See nlsr-derivs.log for more info.
--- failed re-building ‘nlsr-derivs.Rmd’

--- re-building ‘nlsr-devdoc.Rmd’ using rmarkdown
! Undefined control sequence.
l.336 \textless- jj jj \}cat(``try nlfb\n
                                         '')\#\# try nlfb st \textless- 

Error: processing vignette ‘nlsr-devdoc.Rmd’ failed with diagnostics:
LaTeX failed to compile /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/nlsr.Rcheck/vign_test/nlsr/vignettes/nlsr-devdoc.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See nlsr-devdoc.log for more info.
--- failed re-building ‘nlsr-devdoc.Rmd’

--- re-building ‘nlsr-nls-nlsLM.Rmd’ using rmarkdown
pandoc-citeproc: reference param not found
pandoc-citeproc: reference return not found
pandoc-citeproc: reference references not found
pandoc-citeproc: reference examples not found
pandoc-citeproc: reference export not found
! Undefined control sequence.
l.396 \} else \{ cat(sobj," does not exist\n
                                            ") \} \# return(NULL) \}start1 

Error: processing vignette ‘nlsr-nls-nlsLM.Rmd’ failed with diagnostics:
LaTeX failed to compile /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/nlsr.Rcheck/vign_test/nlsr/vignettes/nlsr-nls-nlsLM.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See nlsr-nls-nlsLM.log for more info.
--- failed re-building ‘nlsr-nls-nlsLM.Rmd’

SUMMARY: processing the following files failed:
  ‘nlsr-derivs.Rmd’ ‘nlsr-devdoc.Rmd’ ‘nlsr-nls-nlsLM.Rmd’

Error: Vignette re-building failed.
Execution halted