如何在 lightgbm 和 Python 中绘制学习曲线？

Question

我已经训练了一个 lightgbm 模型，我想绘制学习曲线。我怎样才能做到这一点？在 Keras 示例中，history 返回指标，以便我可以在训练结束后绘制它们。这里是如何处理这个任务的？

我的代码如下：

def f_lgboost(data, params):

    model = lgb.LGBMClassifier(**params)


    X_train = data['X_train']

    y_train = data['y_train']

    X_dev = data['X_dev']

    y_dev = data['y_dev']

    X_test = data['X_test']

    categorical_feature= ['Ticker_code', 'Category_code']

    X_train[categorical_feature] = X_train[categorical_feature].astype('category')

    X_dev[categorical_feature] = X_dev[categorical_feature].astype('category')

    X_test[categorical_feature] = X_test[categorical_feature].astype('category')


    feature_name = X_train.columns.to_list()

    model.fit(X_train, y_train, eval_set = [(X_dev, y_dev)], eval_metric = 'auc', early_stopping_rounds = 20, 
              categorical_feature = categorical_feature, feature_name = feature_name)

    y_pred_train = model.predict_proba(X_train)[:, 1].ravel()

    y_pred_dev = model.predict_proba(X_dev)[:, 1].ravel()

    from sklearn.metrics import roc_auc_score

    auc_train = roc_auc_score(y_train, y_pred_train)

    auc_dev = roc_auc_score(y_dev, y_pred_dev)

    from sklearn.metrics import precision_recall_fscore_support

    precision, recall ,fscore, support = precision_recall_fscore_support(y_dev, (y_pred_dev > 0.5).astype(int), beta=0.5)

    y_pred_test = model.predict_proba(X_test)[:, 1].ravel()

    print(f'auc_train: {auc_train}, auc_dev : {auc_dev}, precision : {precision}, recall: {recall}, fscore : {fscore}')

    Results = {

            'params' : params,

            'data' : data,

            'lg_boost_model' : bst,

            'y_pred_train' : y_pred_train,

            'y_pred_dev' : y_pred_dev,

            'y_pred_test' : y_pred_test,

            'auc_train' : auc_train,

            'auc_dev' : auc_dev,

            'precision_dev': precision,

            'recall_dev' : recall,

            'fscore_dev' : fscore,

            'support_dev' : support


        }


    return Results

Answer 1

在 scikit-learn API 中，学习曲线可通过属性获得lightgbm.LGBMModel.evals_result_。它们将包括使用eval_set方法参数中指定的数据集计算的指标fit（因此您通常希望在那里指定训练集和验证集）。还有内置的绘图函数，lightgbm.plot_metric，它接受model.evals_result_或model直接。

这是一个完整的最小示例：

import lightgbm as lgb
import sklearn.datasets, sklearn.model_selection

X, y = sklearn.datasets.load_boston(return_X_y=True)
X_train, X_val, y_train, y_val = sklearn.model_selection.train_test_split(X, y, random_state=7054)

model = lgb.LGBMRegressor(objective='mse', seed=8798, num_threads=1)
model.fit(X_train, y_train, eval_set=[(X_val, y_val), (X_train, y_train)], verbose=10)

lgb.plot_metric(model)

这是结果图：