Dear Prof. Smith,

　　I am writing this email to express my genuine regret for that I couldn’t be able to visit you as scheduled.

　　To begin with, I do appreciate the invitation from you for the travel under your guidance and the visit to your house. However, I am awfully sorry for the change of plan since I have to attend the wedding ceremony of one of my best friends. I hope that the sudden schedule change would not bring too much inconvenience to you.

　　I would like to propose another arrangement on next Friday afternoon and to see if it is convenient for you. Your prompt attention to my email would be highly appreciated, and I look forward to your reply at your earliest convenience.

　　Sincerely yours,

　　Li Ming