Error(s) in re-building vignettes:
  ...
--- re-building ‘Basic_usage.Rmd’ using rmarkdown
0%   10   20   30   40   50   60   70   80   90   100%
[----|----|----|----|----|----|----|----|----|----|
**************************************************|

Quitting from lines 87-92 [unnamed-chunk-7] (Basic_usage.Rmd)
Error: processing vignette 'Basic_usage.Rmd' failed with diagnostics:
Suggested packages are missing for the plot output.
Please install first the following packages: ggplot2.
Install command: install.packages('ggplot2')
--- failed re-building ‘Basic_usage.Rmd’

--- re-building ‘Topical_time_series.Rmd’ using rmarkdown
** Processing: /home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/sentopics.Rcheck/vign_test/sentopics/vignettes/Topical_time_series_files/figure-html/unnamed-chunk-3-1.png
672x384 pixels, 8 bits/pixel, 256 colors in palette
Reducing image to 8 bits/pixel, grayscale
Input IDAT size = 23100 bytes
Input file size = 23982 bytes

Trying:
  zc = 9  zm = 8  zs = 0  f = 0		IDAT size = 21461
  zc = 9  zm = 8  zs = 1  f = 0
  zc = 1  zm = 8  zs = 2  f = 0
  zc = 9  zm = 8  zs = 3  f = 0
  zc = 9  zm = 8  zs = 0  f = 5		IDAT size = 19426
  zc = 9  zm = 8  zs = 1  f = 5
  zc = 1  zm = 8  zs = 2  f = 5
  zc = 9  zm = 8  zs = 3  f = 5
                               
Selecting parameters:
  zc = 9  zm = 8  zs = 0  f = 5		IDAT size = 19426

Output IDAT size = 19426 bytes (3674 bytes decrease)
Output file size = 19504 bytes (4478 bytes = 18.67% decrease)

0%   10   20   30   40   50   60   70   80   90   100%
[----|----|----|----|----|----|----|----|----|----|
**************************************************|

Quitting from lines 103-104 [unnamed-chunk-10] (Topical_time_series.Rmd)
Error: processing vignette 'Topical_time_series.Rmd' failed with diagnostics:
Suggested packages are missing for the sentiment_breakdown function.
Please install first the following packages: ggplot2.
Install command: install.packages('ggplot2')
--- failed re-building ‘Topical_time_series.Rmd’

SUMMARY: processing the following files failed:
  ‘Basic_usage.Rmd’ ‘Topical_time_series.Rmd’

Error: Vignette re-building failed.
Execution halted