thanks for your reply. I did, but still not working. I even updated my os to refresh the xcode.
Do you want to attempt to install these from sources? (Yes/no/cancel) no
| Could not install package ‘readr’!
| | 0%Error in seq.default(0, 1, length.out = nrow(e$les)) :
argument 'length.out' must be of length 1
| Leaving swirl now. Type swirl() to resume.