ValueError : when array length doesn't match index length. How to debug this?

Question

所以我开始使用 Kaggle 并且我正在做预测谁在泰坦尼克号坠毁中幸存下来以及谁没有幸存的指导性任务。

我按照要求做了所有事情。

所以我的最后一个代码单元看起来像这样

from sklearn.ensemble import RandomForestClassifier

y = train_data['Survived']
features = ["Pclass","Sex","SibSp","Parch"]
X = pd.get_dummies(train_data[features])
X_test = pd.get_dummies(train_data[features])
model = RandomForestClassifier(n_estimators=1,max_depth=5,random_state=1)
model.fit(X,y)
predictions = model.predict(X_test)



output = pd.DataFrame({'PassengerId': test_data.PassengerId, 'Survived': predictions})
output.to_csv('my_submission.csv', index=False)
print("Your submission was successfully saved!")

编译后显示以下错误：

ValueError                                Traceback (most recent call last)
<ipython-input-24-7d2fc2ea2973> in <module>
     11 
     12 
---> 13 output = pd.DataFrame({'PassengerId': test_data.PassengerId, 'Survived': predictions})
     14 output.to_csv('my_submission.csv', index=False)
     15 print("Your submission was successfully saved!")

/opt/conda/lib/python3.7/site-packages/pandas/core/frame.py in __init__(self, data, index, columns, dtype, copy)
    433             )
    434         elif isinstance(data, dict):
--> 435             mgr = init_dict(data, index, columns, dtype=dtype)
    436         elif isinstance(data, ma.MaskedArray):
    437             import numpy.ma.mrecords as mrecords

/opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in init_dict(data, index, columns, dtype)
    252             arr if not is_datetime64tz_dtype(arr) else arr.copy() for arr in arrays
    253         ]
--> 254     return arrays_to_mgr(arrays, data_names, index, columns, dtype=dtype)
    255 
    256 

/opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in arrays_to_mgr(arrays, arr_names, index, columns, dtype)
     62     # figure out the index, if necessary
     63     if index is None:
---> 64         index = extract_index(arrays)
     65     else:
     66         index = ensure_index(index)

/opt/conda/lib/python3.7/site-packages/pandas/core/internals/construction.py in extract_index(data)
    376                         f"length {len(index)}"
    377                     )
--> 378                     raise ValueError(msg)
    379             else:
    380                 index = ibase.default_index(lengths[0])

ValueError: array length 891 does not match index length 418

但是，我无法调试我的错误到底是什么，有人可以帮忙吗？谢谢。

Answer 1

您构建 X_test 数据框的方式不正确，一旦您考虑 train_data，而不是 test_data。在创建输出文件时，这会在 test_data.PassengerId 和 predictions 的大小之间造成不匹配。

更正以下行，它将起作用：

X_test = pd.get_dummies(test_data[features])

Answer 2

纠正 x_test 赋值，将 x_train 替换为 x_test。

ValueError : when array length doesn't match index length. How to debug this?

ValueError : when array length doesn't match index length. How to debug this?

python

machine-learning

pandas

data-science

kaggle