Trouble executing the MCMCpack on R - r

Question

I have installed the 'MCMCpack' package on my R using the code install.packages("MCMCpack") successfully.
also installing the dependency ‘quantreg’
There are binary versions available but the source versions are later:
binary source needs_compilation
quantreg 5.85 5.94 TRUE
MCMCpack 1.6-0 1.6-3 TRUE
Do you want to install from sources the packages which need compilation? (Yes/no/cancel) Yes
installing the source packages ‘quantreg’, ‘MCMCpack’
trying URL 'https://cran.rstudio.com/src/contrib/quantreg_5.94.tar.gz'
Content type 'application/x-gzip' length 1025290 bytes (1001 KB)
==================================================
downloaded 1001 KB
trying URL 'https://cran.rstudio.com/src/contrib/MCMCpack_1.6-3.tar.gz'
Content type 'application/x-gzip' length 1030533 bytes (1006 KB)
==================================================
downloaded 1006 KB
* installing *source* package ‘quantreg’ ...
** package ‘quantreg’ successfully unpacked and MD5 sums checked
** using staged installation
** libs
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
ERROR: compilation failed for package ‘quantreg’
* removing ‘/Library/Frameworks/R.framework/Versions/3.6/Resources/library/quantreg’
Warning in install.packages :
installation of package ‘quantreg’ had non-zero exit status
ERROR: dependency ‘quantreg’ is not available for package ‘MCMCpack’
* removing ‘/Library/Frameworks/R.framework/Versions/3.6/Resources/library/MCMCpack’
Warning in install.packages :
installation of package ‘MCMCpack’ had non-zero exit status
The downloaded source packages are in
‘/private/var/folders/xp/077px4z927d5jplc0wg9701r0000gn/T/RtmpAgOlHz/downloaded_packages’
But when I enter library(MCMCpack), it returns this error message:
Error in library("MCMCpack") : there is no package called ‘MCMCpack’
What might be the problem here? There seems no issue in installing the package beforehand.

Answer 1

I have installed the 'MCMCpack' package on my R using the code install.packages("MCMCpack") successfully.
No, your installation of MCMCpack was unsuccessful, as is clearly indicated by the error & warning messages.
Of note,
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
This is usually the result of the Command Line Tools not having been installed (correctly). You can install the Xcode Command Line Tools with
xcode-select --install
Then re-issue
install.packages("MCMCpack")