I know similar qquestions have been asked before but all the suggested solutions I read about and that worked for other users failed in my case... I was suddenly no longer able to install R packages on my R version 3.3. and received the following error messsage:
Warning in install.packages : unable to access index for repository http://cran.univ-paris1.fr src/contrib: cannot open URL 'http://cran.univ-paris1.fr/src/contrib/PACKAGES' Warning in install.packages
I already tried several different mirrors which did not work. I even updated my R to the newest version (3.5.1) which also did not help. I changed the general options and unselected "secure download method for HTTP" and also "use internet explorer library/proxy for http")- without any success. Lastely, I was running "options(repos="my_favorite_CRAN_mirror")" before trying to install a package but it also failed.
Does anyone have an idea what else I could try? Any help would be highly appreciated!!! Thanks a lot!