R: Callback closure for logging the evaluation history

cb.evaluation.log {xgboost} | R Documentation

## Callback closure for logging the evaluation history

### Description

Callback closure for logging the evaluation history

### Usage

    cb.evaluation.log()

### Details

This callback function appends the current iteration evaluation results `bst_evaluation` available in the calling parent frame to the `evaluation_log` list in a calling frame.

The finalizer callback (called with `finalize = TURE` in the end) converts the `evaluation_log` list into a final data.table.

The iteration evaluation result `bst_evaluation` must be a named numeric vector.

Note: in the column names of the final data.table, the dash '-' character is replaced with the underscore '_' in order to make the column names more like regular R identifiers.

Callback function expects the following values to be set in its calling frame: `evaluation_log`, `bst_evaluation`, `iteration`.

### See Also

`callbacks`

[Package xgboost version 1.5.1.1 Index]