R是由自制软件安装的，这里是 R版本3.2.3（2015-12-10） 平台：x86_64-apple-darwin15.2.0（64位） 运行于：OS X 10.11（El Capitan）
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
other attached packages:
[1] dplyr_0.4.3
loaded via a namespace (and not attached):
[1] magrittr_1.5 R6_2.1.1 assertthat_0.1 parallel_3.2.3 DBI_0.3.1 tools_3.2.3 Rcpp_0.12.2
当我尝试安装'png'时，它会返回以下消息：
Installing package into ‘/usr/local/lib/R/3.2/site-library’
(as ‘lib’ is unspecified)
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0 0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0100 24990 100 24990 0 0 32041 0 --:--:-- --:--:-- --:--:-- 32038
* installing *source* package ‘png’ ...
** package ‘png’ successfully unpacked and MD5 sums checked
** libs
clang -I/usr/local/Cellar/r/3.2.3/R.framework/Resources/include -DNDEBUG -I/usr/local/include -I/ usr/local/opt/gettext/include -I/usr/local/opt/readline/include -I/usr/local/opt/openssl/include -I /usr/local/opt/jpeg/include -I/usr/local/include `libpng-config --cflags` -fPIC -I/usr/local/ opt/gsl/include -c read.c -o read.o
clang -I/usr/local/Cellar/r/3.2.3/R.framework/Resources/include -DNDEBUG -I/usr/local/include -I/ usr/local/opt/gettext/include -I/usr/local/opt/readline/include -I/usr/local/opt/openssl/include -I /usr/local/opt/jpeg/include -I/usr/local/include `libpng-config --cflags` -fPIC -I/usr/local/ opt/gsl/include -c write.c -o write.o
clang -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module - multiply_defined suppress -L/usr/local/Cellar/r/3.2.3/R.framework/Resources/lib -L/usr/local/opt/ gettext/lib -L/usr/local/opt/readline/lib -L/usr/local/opt/openssl/lib -L/usr/local/opt/jpeg/ -L/ usr/local/opt/gsl/lib -lgsl -lgslcblas -o png.so read.o write.o -L/usr/local/opt/gettext/lib -F/usr /local/Cellar/r/3.2.3/R.framework/.. -framework R -lintl -Wl,-framework -Wl,CoreFoundation
installing to /usr/local/lib/R/3.2/site-library/png/libs
** R
** inst
** preparing package for lazy loading
** help
*** installing help indices
** building package indices
** testing if installed package can be loaded
Error in dyn.load(file, DLLpath = DLLpath, ...) :
unable to load shared object '/usr/local/lib/R/3.2/site-library/png/libs/png.so':
dlopen(/usr/local/lib/R/3.2/site-library/png/libs/png.so, 6): Symbol not found: _png_create_info_struct
Referenced from: /usr/local/lib/R/3.2/site-library/png/libs/png.so
Expected in: flat namespace
in /usr/local/lib/R/3.2/site-library/png/libs/png.so
Error: loading failed
Execution halted
ERROR: loading failed
* removing ‘/usr/local/lib/R/3.2/site-library/png’
Warning in install.packages :
installation of package ‘png’ had non-zero exit status
The downloaded source packages are in
‘/private/var/folders/h4/1wm7nk_x05d0s_nzd1bgh84c0000gn/T/Rtmpcfpi82/downloaded_packages’
看起来libpng安装不正确。所以我用自制软件重新安装它，但这个问题仍然存在。我试图从源代码安装它，但也失败了。
另外，我无法安装软件包'jpeg'，错误信息与上面的类似：'找不到符号：_jpeg_CreateCompress'。