See the error: ld: library not found for -lgfortran
You need to install the Fortran libraries as RcppArmadillo has this in src/Makevars
:
PKG_LIBS=`$(R_HOME)/bin/Rscript -e "Rcpp:::LdFlags()"` \
$(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
You get Lapack and Blas via R, but need the Fortran libs. See the OS X documentation for R about where to get this; I believe the place is Simon's page at AT&T but I am not an OS X user myself. If in doubt, ask on r-sig-mac where there are also numerous discussion threads concerning the various breakages which occurred with upgrades to OS X 10.9.