# cb.reset.parameters

##### Callback closure for restetting the booster's parameters at each iteration.

Callback closure for restetting the booster's parameters at each iteration.

##### Usage

`cb.reset.parameters(new_params)`

##### Arguments

- new_params
a list where each element corresponds to a parameter that needs to be reset. Each element's value must be either a vector of values of length

`nrounds`

to be set at each iteration, or a function of two parameters`learning_rates(iteration, nrounds)`

which returns a new parameter value by using the current iteration number and the total number of boosting rounds.

##### Details

This is a "pre-iteration" callback function used to reset booster's parameters at the beginning of each iteration.

Note that when training is resumed from some previous model, and a function is used to
reset a parameter value, the `nround`

argument in this function would be the
the number of boosting rounds in the current training.

Callback function expects the following values to be set in its calling frame:
`bst`

or `bst_folds`

,
`iteration`

,
`begin_iteration`

,
`end_iteration`

.

##### See Also

*Documentation reproduced from package xgboost, version 0.6.4.1, License: Apache License (== 2.0) | file LICENSE*