Those functions are low-level functions used by `errorest`

and
are normally not called by users.

```
# S3 method for factor
cv(y, formula, data, model, predict, k=10, random=TRUE,
strat=FALSE,
predictions=NULL, getmodels=NULL, list.tindx = NULL, ...)
```

- y
response variable, either of class

`factor`

(classification),`numeric`

(regression) or`Surv`

(survival).- formula
a formula object.

- data
data frame of predictors and response described in

`formula`

.- model
a function implementing the predictive model to be evaluated. The function

`model`

can either return an object representing a fitted model or a function with argument`newdata`

which returns predicted values. In this case, the`predict`

argument to`errorest`

is ignored.- predict
a function with arguments

`object`

and`newdata`

only which predicts the status of the observations in`newdata`

based on the fitted model in`object`

.- k
k-fold cross-validation.

- random
logical, indicates whether a random order or the given order of the data should be used for sample splitting or not, defaults to

`TRUE`

.- strat
logical, stratified sampling or not, defaults to

`FALSE`

.- predictions
logical, return the prediction of each observation.

- getmodels
logical, return a list of models for each fold.

- list.tindx
list of numeric vectors, indicating which observations are included in each cross-validation sample.

- ...
additional arguments to

`model`

.

See `errorest`

.