当我在运行时尝试使用y_train时，出现了ValueError错误。我检查了y_test和y_train的形状，发现其中一个是(2000,)，而另一个不是。有什么方法可以修复这个错误呢？

import pandas as pddf = pd.read_csv('iris.csv')df.head()df.shapedf.loc[df["species"] == "setosa", "species"] = 0df.loc[df["species"] == "versicolor", "species"] = 1df.loc[df["species"] == "virginica", "species"] = 2from sklearn.model_selection import train_test_splitX=df.drop('species',axis=1)y=df['species']X_train, X_test, y_train, y_test = train_test_split(X, y,test_size=0.2, random_state=156)from sklearn.tree import DecisionTreeClassifiermy_model = DecisionTreeClassifier(random_state=0)result = my_model.fit(X_train,y_train)

回答：

您的方法如下：

df.loc[df["species"] == "setosa", "species"] = 0df.loc[df["species"] == "versicolor", "species"] = 1df.loc[df["species"] == "virginica", "species"] = 2

使得df['species']成为object类型，这不被DecisionTreeClassifier所支持。相反，您应该这样做：

df['species'] = df['species'].map({'setosa':0, 'versicolor':1, 'virginica':2})