I am having trouble running aplpack on my Mac. It will run on my PC, but the Mac gives an error message. Below is the result that I obtained. It seems to install fine--see below--but I can't load the library. > install.packages("aplpack") trying URL 'http://cran.rstudio.com/bin/macosx/contrib/3.1/aplpack_1.3.0.tgz' Content type 'application/x-gzip' length 3157548 bytes (3.0 Mb) opened URL =================================================downloaded 3.0 Mb The downloaded binary packages are in /var/folders/6m/t4wvnh9x39500z_rh3p5jlk00000gp/T//Rtmp26I5Ej/downloaded_packages > library(aplpack) Loading required package: tcltk xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun It looks as if it has a problem with tcltk. I can install tcltk2, but when I try to install tcltk it tells me "package not found.) Is that the problem that aplpack is having when it tries to load the library? Any suggestions?