I'm trying to do a discriminant analysis. My data do not have normality or homocedasticity, therefore, I can not do a linear discriminant analysis, but my database is small, therefore, I can not do a quadratic discriminant analysis either. I thought that my best option is a regularized discriminant analysis, but I can not find a way to estimate the optimal values for lambda and gamma according to my database. I understand the way they influence, but I can not find a way to estimate the optimal values. Or are the values used in the author's opinion without the estimation methodology?