anchor.diff:  RUN rm \
      openintro_1.7.1.tar.gz \
      assertthat_0.2.0.tar.gz \
  -   R6_2.2.2.tar.gz \
      magrittr_1.5.tar.gz \
      lazyeval_0.2.1.tar.gz \
      DBI_1.0.0.tar.gz \
  
positive.code: RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
     openintro_1.7.1.tar.gz \
     assertthat_0.2.0.tar.gz \
     R6_2.2.2.tar.gz \
     magrittr_1.5.tar.gz \
     lazyeval_0.2.1.tar.gz \
     DBI_1.0.0.tar.gz \
  
negative.code:    https://archive.linux.duke.edu/cran/src/contrib/tidyselect_0.2.4.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/dplyr_0.7.6.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/assertthat_0.2.0.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/magrittr_1.5.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/lazyeval_0.2.1.tar.gz \
     https://archive.linux.duke.edu/cran/src/contrib/DBI_1.0.0.tar.gz 
  