我有一个数据框架形式的相当大的数据集,我想知道我如何能够将数据框架分成两个随机样本(80%和20%)进行训练和测试。

谢谢!


当前回答

您可以使用df.as_matrix()函数并创建Numpy-array并传递它。

Y = df.pop()
X = df.as_matrix()
x_train, x_test, y_train, y_test = train_test_split(X, Y, test_size = 0.2)
model.fit(x_train, y_train)
model.test(x_test)

其他回答

这是我在需要分割数据帧时所写的。我考虑过使用上面安迪的方法,但不喜欢我不能精确地控制数据集的大小(例如,有时是79,有时是81,等等)。

def make_sets(data_df, test_portion):
    import random as rnd

    tot_ix = range(len(data_df))
    test_ix = sort(rnd.sample(tot_ix, int(test_portion * len(data_df))))
    train_ix = list(set(tot_ix) ^ set(test_ix))

    test_df = data_df.ix[test_ix]
    train_df = data_df.ix[train_ix]

    return train_df, test_df


train_df, test_df = make_sets(data_df, 0.2)
test_df.head()

熊猫随机抽样也可以

train=df.sample(frac=0.8,random_state=200)
test=df.drop(train.index)

对于相同的random_state值,您将始终在训练集和测试集中获得相同的确切数据。这带来了一定程度的可重复性,同时还随机分离训练和测试数据。

有许多方法可以创建训练/测试甚至验证样本。

案例1:没有任何选项的经典方法train_test_split:

from sklearn.model_selection import train_test_split
train, test = train_test_split(df, test_size=0.3)

案例2:非常小的数据集(<500行):为了通过这种交叉验证获得所有行的结果。最后,您将对可用训练集的每一行都有一个预测。

from sklearn.model_selection import KFold
kf = KFold(n_splits=10, random_state=0)
y_hat_all = []
for train_index, test_index in kf.split(X, y):
    reg = RandomForestRegressor(n_estimators=50, random_state=0)
    X_train, X_test = X[train_index], X[test_index]
    y_train, y_test = y[train_index], y[test_index]
    clf = reg.fit(X_train, y_train)
    y_hat = clf.predict(X_test)
    y_hat_all.append(y_hat)

案例3a:用于分类的不平衡数据集。下面是情形1的等价解:

from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, stratify=y, test_size=0.3)

案例3b:用于分类的不平衡数据集。在情形2之后,等价解如下:

from sklearn.model_selection import StratifiedKFold
kf = StratifiedKFold(n_splits=10, random_state=0)
y_hat_all = []
for train_index, test_index in kf.split(X, y):
    reg = RandomForestRegressor(n_estimators=50, random_state=0)
    X_train, X_test = X[train_index], X[test_index]
    y_train, y_test = y[train_index], y[test_index]
    clf = reg.fit(X_train, y_train)
    y_hat = clf.predict(X_test)
    y_hat_all.append(y_hat)

案例4:你需要在大数据上创建一个训练/测试/验证集来调优超参数(60%训练,20%测试和20% val)。

from sklearn.model_selection import train_test_split
X_train, X_test_val, y_train, y_test_val = train_test_split(X, y, test_size=0.6)
X_test, X_val, y_test, y_val = train_test_split(X_test_val, y_test_val, stratify=y, test_size=0.5)

我会用K-fold交叉验证。 它已被证明比train_test_split提供更好的结果。下面是一篇关于如何在sklearn中应用它的文章,来自文档本身:https://scikit-learn.org/stable/modules/generated/sklearn.model_selection.KFold.html

像这样从df中选择range row

row_count = df.shape[0]
split_point = int(row_count*1/5)
test_data, train_data = df[:split_point], df[split_point:]