I tried to install the basic packages and I could not. I kindly ask you to help me to find out the problem. thanks. I followed those:
install.packages("lubridate")
Warning in install.packages :
unable to access index for repository https://cran. rstudio.com/src/contrib:
cannot open URL
The message is telling you that R is not being able to connect to the CRAN repository, is your internet connection behind a proxy server or firewall? That is usually the case when you are at work or school.