I am a student at Ghent University and we have some assignments where we have to use R in RStudio. To start, we have to load some packages. The "pastecs" package works fine for example but then I want to install the package "psych" by:
and it gives following error:
Loading required package: psych
also installing the dependency ‘mnormt’
Warning in install.packages :
unable to access index for repository https://cran.rstudio.com/bin/macosx/el-capitan/contrib/3.6:
cannot open URL 'https://cran.rstudio.com/bin/macosx/el-capitan/contrib/3.6/PACKAGES'
Package which is only available in source form, and may need compilation of C/C++/Fortran: ‘mnormt’
Do you want to attempt to install these from sources? (Yes/no/cancel)
If I answer "yes" it doesn't work either. Thanks in advance!