Error(s) in re-building vignettes:
--- re-building 'about.Rmd' using rmarkdown
--- finished re-building 'about.Rmd'

--- re-building 'case-1-pleiotropy.Rmd' using rmarkdown

Attaching package: 'dplyr'

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

    filter, lag

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

    intersect, setdiff, setequal, union


Attaching package: 'purrr'

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

    set_names


Attaching package: 'glue'

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

    collapse

Quitting from lines 46-52 (case-1-pleiotropy.Rmd) 
Error: processing vignette 'case-1-pleiotropy.Rmd' failed with diagnostics:
there is no package called 'igraph'
--- failed re-building 'case-1-pleiotropy.Rmd'

--- re-building 'case-2-alt-drug-target.Rmd' using rmarkdown
--- finished re-building 'case-2-alt-drug-target.Rmd'

--- re-building 'case-3-literature-triangulation.Rmd' using rmarkdown
Quitting from lines 46-53 (case-3-literature-triangulation.Rmd) 
Error: processing vignette 'case-3-literature-triangulation.Rmd' failed with diagnostics:
there is no package called 'igraph'
--- failed re-building 'case-3-literature-triangulation.Rmd'

--- re-building 'getting-started-with-epigraphdb-r.Rmd' using rmarkdown
--- finished re-building 'getting-started-with-epigraphdb-r.Rmd'

--- re-building 'meta-functionalities.Rmd' using rmarkdown
Quitting from lines 39-44 (meta-functionalities.Rmd) 
Error: processing vignette 'meta-functionalities.Rmd' failed with diagnostics:
there is no package called 'igraph'
--- failed re-building 'meta-functionalities.Rmd'

--- re-building 'options.Rmd' using rmarkdown
--- finished re-building 'options.Rmd'

--- re-building 'using-epigraphdb-api.Rmd' using rmarkdown
--- finished re-building 'using-epigraphdb-api.Rmd'

--- re-building 'using-epigraphdb-r-package.Rmd' using rmarkdown
--- finished re-building 'using-epigraphdb-r-package.Rmd'

SUMMARY: processing the following files failed:
  'case-1-pleiotropy.Rmd' 'case-3-literature-triangulation.Rmd'
  'meta-functionalities.Rmd'

Error: Vignette re-building failed.
Execution halted