Validate gaussian process regression model with leave-one-out cross validation

Dear all,

I have a dataset with:

X = Torque (the input variable)

Y1 = Response 1

Y2 = Response 2

Y3 = Response 3

I want to use the method of leave-one-out cross-validation (LOOCV) to validate the gaussian process regression model. Then, I want to asses the quality of the model by using the root mean squared error (RMSE) and coefficient of determination (R2). How can I do this?