title: k-fold cross validation - how to get the prediction automatically?
body: <p>This may be a silly question but I just can't find a package to do that...I know I can write some codes to get what I want but it would be nice to have a function to do it automatically!</p>
  
  <p>So basically I want to do a k-fold cross-validation for a glm model. I want to automatically get the predictions of each validation set and the actual value too. So if I am doing a 10-fold CV, I want a function to return the 10 validation sets with the actual responses and  predictions all together. </p>
  
  <p>Thank you in advance!</p>