R: Get record evaluation result from booster

lgb.get.eval.result {lightgbm} | R Documentation

## Get record evaluation result from booster

### Description

Given a `lgb.Booster`, return evaluation results for a particular metric on a particular dataset.

### Usage

    lgb.get.eval.result(
      booster,
      data_name,
      eval_name,
      iters = NULL,
      is_err = FALSE
    )

### Arguments

`booster` | Object of class `lgb.Booster`
`data_name` | Name of the dataset to return evaluation results for.
`eval_name` | Name of the evaluation metric to return results for.
`iters` | An integer vector of iterations you want to get evaluation results for. If NULL (the default), evaluation results for all iterations will be returned.
`is_err` | TRUE will return evaluation error instead

### Value

numeric vector of evaluation result

### Examples

    # train a regression model
    data(agaricus.train, package = "lightgbm")
    train <- agaricus.train
    dtrain <- lgb.Dataset(train$data, label = train$label)
    data(agaricus.test, package = "lightgbm")
    test <- agaricus.test
    dtest <- lgb.Dataset.create.valid(dtrain, test$data, label = test$label)
    params <- list(
      objective = "regression"
      , metric = "l2"
      , min_data = 1L
      , learning_rate = 1.0
    )
    valids <- list(test = dtest)
    model <- lgb.train(
      params = params
      , data = dtrain
      , nrounds = 5L
      , valids = valids
    )

    # Examine valid data_name values
    print(setdiff(names(model$record_evals), "start_iter"))

    # Examine valid eval_name values for dataset "test"
    print(names(model$record_evals[["test"]]))

    # Get L2 values for "test" dataset
    lgb.get.eval.result(model, "test", "l2")

[Package lightgbm version 3.3.2 Index]