anchor.diff:  
   RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
      lubridate_1.7.4.tar.gz  \
  -   gtable_0.2.0.tar.gz \
  +   gtable_0.3.0.tar.gz \
      RColorBrewer_1.1-2.tar.gz \
      dichromat_2.0-0.tar.gz \
      colorspace_1.4-1.tar.gz \
  
positive.code:    https://archive.linux.duke.edu/cran/src/contrib/scales_1.0.0.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/stargazer_5.2.2.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/reshape2_1.4.3.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/gtable_0.2.0.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/proto_1.0.0.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/minqa_1.2.4.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/RcppEigen_0.3.3.5.0.tar.gz \
  
negative.code: 
  RUN rm \
     lubridate_1.7.4.tar.gz  \
     gtable_0.3.0.tar.gz \
     RColorBrewer_1.1-2.tar.gz \
     dichromat_2.0-0.tar.gz \
     colorspace_1.4-1.tar.gz \
  