anchor.diff:  FROM  ubuntu:20.04
   
  -RUN echo 'force complete rebuild'
  +RUN echo 'force a complete rebuild'
   
   # install R
   RUN apt update 
  
positive.code: #
  #########
  
  # expose the RStudio IDE port
  EXPOSE 8787 
  
  
negative.code: 
  # R-Studio
  RUN DEBIAN_FRONTEND=noninteractive apt-get install -y gdebi-core
  #RUN DEBIAN_FRONTEND=noninteractive wget https://download2.rstudio.org/server/bionic/amd64/rstudio-server-1.4.1717-amd64.deb
  #RUN DEBIAN_FRONTEND=noninteractive gdebi --n rstudio-server-1.4.1717-amd64.deb
  RUN DEBIAN_FRONTEND=noninteractive wget https://download2.rstudio.org/server/bionic/amd64/rstudio-server-1.3.1056-amd64.deb
  RUN DEBIAN_FRONTEND=noninteractive gdebi --n rstudio-server-1.3.1056-amd64.deb
  RUN rm rstudio-server-1.3.1056-amd64.deb
     
  # install packages via R scripts found in conf directory
  ADD ./conf /r-studio   
  