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

Quitting from flowchart.Rmd:115-120 [unnamed-chunk-9]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<error/dplyr:::mutate_error>
Error in `dplyr::mutate()`:
ℹ In argument: `y = update_y(.data$y, .data$type, .data$x,
  .data$group)`.
ℹ In row 1.
Caused by error in `dplyr::mutate()`:
ℹ In argument: `nmax = as.numeric(...)`.
ℹ In row 1.
Caused by error in `xtfrm.data.frame()`:
! cannot xtfrm data frames
---
Backtrace:
     ▆
  1. ├─flowchart::fc_draw(...)
  2. │ └─flowchart:::is_class(object, "fc")
  3. ├─flowchart::fc_filter(...)
  4. ├─flowchart:::fc_filter.fc(...)
  5. │ ├─dplyr::mutate(...)
  6. │ └─dplyr:::mutate.data.frame(...)
  7. │   └─dplyr:::mutate_cols(.data, dplyr_quosures(...), by)
  8. │     ├─base::withCallingHandlers(...)
  9. │     └─dplyr:::mutate_col(dots[[i]], data, mask, new_columns)
 10. │       └─mask$eval_all_mutate(quo)
 11. │         └─dplyr (local) eval()
 12. ├─flowchart:::update_y(.data$y, .data$type, .data$x, .data$group)
 13. │ ├─dplyr::mutate(...)
 14. │ └─dplyr:::mutate.data.frame(...)
 15. │   └─dplyr:::mutate_cols(.data, dplyr_quosures(...), by)
 16. │     ├─base::withCallingHandlers(...)
 17. │     └─dplyr:::mutate_col(dots[[i]], data, mask, new_columns)
 18. │       └─mask$eval_all_mutate(quo)
 19. │         └─dplyr (local) eval()
 20. └─base::which.max(...)
 21.   ├─base::xtfrm(`<tibble[,1]>`)
 22.   └─base::xtfrm.data.frame(`<tibble[,1]>`)
 23.     └─base::stop("cannot xtfrm data frames")
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Error: processing vignette 'flowchart.Rmd' failed with diagnostics:
ℹ In argument: `y = update_y(.data$y, .data$type, .data$x,
  .data$group)`.
ℹ In row 1.
Caused by error in `dplyr::mutate()`:
ℹ In argument: `nmax = as.numeric(...)`.
ℹ In row 1.
Caused by error in `xtfrm.data.frame()`:
! cannot xtfrm data frames
--- failed re-building ‘flowchart.Rmd’

SUMMARY: processing the following file failed:
  ‘flowchart.Rmd’

Error: Vignette re-building failed.
Execution halted