anchor.diff:  
   # 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-1.4.1717-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   
  
positive.code: FROM  ubuntu:20.04
  
  RUN echo 'force complete rebuild'
  
  # install R
  RUN apt update 
  
negative.code: #
  #########
  
  
  RUN apt-get autoremove -y
  RUN apt-get clean
  
  # expose the RStudio IDE port
  EXPOSE 8787 
  
  