I have a problem with SVM classification plot error: “‘min’ not meaningful for factors”)

Question

I am plotting a SVM model for 12 vowels. There will be 12 classes. My file is https://docs.google.com/spreadsheets/d/1eXQ7mq7bm8yFdBaUrijCUsLGS9nFlhb37esA8p61ZyM/edit?usp=sh