I am trying to install samr package on a macOS system R v3.4, but I get this warning message "Warning in install.packages :
  installation of package ‘samr’ had non-zero exit status. 

Consequently, R doesn't recognize the command library(samr)

What should I do to handle this problem ?

thanks 

T

Here is the full warning message:

Package which is only available in source form, and may need compilation of
  C/C++/Fortran: ‘samr’
Do you want to attempt to install these from sources?
y/n: y
installing the source package ‘samr’

trying URL 'https://cran.rstudio.com/src/contrib/samr_2.0.tar.gz'
Content type 'application/x-gzip' length 36702 bytes (35 KB)
==================================================
downloaded 35 KB

* installing *source* package ‘samr’ ...
** libs
gfortran   -fPIC  -g -O2  -c rankcol.f -o rankcol.o
make: gfortran: No such file or directory
make: *** [rankcol.o] Error 1
ERROR: compilation failed for package ‘samr’
* removing ‘/Library/Frameworks/R.framework/Versions/3.4/Resources/library/samr’
Warning in install.packages :
  installation of package ‘samr’ had non-zero exit status

Possible solutions:

1.) Be sure you have the latest version of xcode installed before installing R packages from source.

2.) The following answer on stackoverflow may be a solution to your problem: https://stackoverflow.com/a/37754162