Funtion to fit with x and y and x_U. Function calcule y with NA values and append in y param
# S3 method for model_sslr
fit_x_u(object, x = NULL, y = NULL, x_U = NULL, ...)
is the model
is a data frame or matrix with train dataset without objective feature. X only have labeled data
is objective feature with labeled values
train unlabeled data without objective feature
This parameter is included for compatibility reasons.