Error(s) in re-building vignettes:
  ...
--- re-building 'international-mortality-tables-overview.Rmd' using rmarkdown
Quitting from lines 235-237 (international-mortality-tables-overview.Rmd) 
Error: processing vignette 'international-mortality-tables-overview.Rmd' failed with diagnostics:
could not find function "whittaker"
--- failed re-building 'international-mortality-tables-overview.Rmd'

--- re-building 'using-the-mortalityTables-package.Rmd' using rmarkdown

(process:6878): Pango-WARNING **: 16:38:16.729: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.751: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.753: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.754: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.773: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.774: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.775: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.776: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.778: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.779: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.842: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.844: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.845: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.846: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.848: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:16.850: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.181: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.182: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.184: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.185: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.191: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.192: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.194: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.195: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.197: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.198: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.264: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.265: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.266: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.267: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.269: Invalid UTF-8 string passed to pango_layout_set_text()

(process:6878): Pango-WARNING **: 16:38:17.271: Invalid UTF-8 string passed to pango_layout_set_text()
--- finished re-building 'using-the-mortalityTables-package.Rmd'

SUMMARY: processing the following file failed:
  'international-mortality-tables-overview.Rmd'

Error: Vignette re-building failed.
Execution halted