[R] validate() in Design library

[array chip]

Hi, another question about validate() in Design library. The arugment "B" of this function is number of repetition for method="bootstrap", which is easy to understand; but for method="crossvalidation", B is the number of groups of omitted observations. This is confusing, I don't understand what it means. Let's say 5-fold cross validation, all samples are divided into 5 groups of equal number of samples, 4 groups will be used as training and the model developed there will be tested in the 1 group left-over. And the process circulate for all 5 groups. What does the "B" argument mean in this example? B=5? or B=1 because 1 group of samples omitted from model development?

Thanks

Yi