anchor.diff:  RUN DEBIAN_FRONTEND=noninteractive R CMD INSTALL \
      chron_2.3-47.tar.gz \
      data.table_1.9.6.tar.gz \
  +   rematch_1.0.1.tar.gz \
      cellranger_1.1.0.tar.gz \
      tidyr_0.5.1.tar.gz \
      readr_1.0.0.tar.gz \
  
positive.code: RUN DEBIAN_FRONTEND=noninteractive wget \
     http://archive.linux.duke.edu/cran/src/contrib/chron_2.3-47.tar.gz \
     http://archive.linux.duke.edu/cran/src/contrib/data.table_1.9.6.tar.gz \
     http://archive.linux.duke.edu/cran/src/contrib/cellranger_1.1.0.tar.gz \
     http://archive.linux.duke.edu/cran/src/contrib/tidyr_0.5.1.tar.gz \
     http://archive.linux.duke.edu/cran/src/contrib/googlesheets_0.2.1.tar.gz \
  
negative.code: RUN rm \
     chron_2.3-47.tar.gz \
     data.table_1.9.6.tar.gz \
     rematch_1.0.1.tar.gz \
     cellranger_1.1.0.tar.gz \
     tidyr_0.5.1.tar.gz \
     googlesheets_0.2.1.tar.gz \
  