helloworld.md

# Hello World

HelloWorld, 请阅读如下代码：

```python
import numpy as np

def test():
    X = np.array([[1, 1], [1, 2], [2, 2], [2, 3]])
    y = np.dot(X, np.array([1, 2])) + 3

    // TODO(选择选项中的代码填充此处)

    y_predict = reg.predict(np.array([[3, 5]]))
    print(y_predict)

if __name__ == '__main__':
    test()
```

若将以下选项中的代码分别填充到上述代码中**TODO**处，哪个选项不是线性模型？

## template

```java
import numpy as np

def test():
    X = np.array([[1, 1], [1, 2], [2, 2], [2, 3]])
    y = np.dot(X, np.array([1, 2])) + 3

    // 下面的 code 占位符会被替换成答案和选项代码
    $code

    y_predict = reg.predict(np.array([[3, 5]]))
    print(y_predict)

if __name__ == '__main__':
    test()
```


## 答案

```python
from sklearn import svm
reg = svm.SVC(kernel='rbf').fit(X, y)
```

## 选项

### 使用 LinearRegression

```python
from sklearn.linear_model import LinearRegression
reg = LinearRegression().fit(X, y)
```

### 使用岭回归

```python
from sklearn.linear_model import Ridge
reg = Ridge(alpha=0.1)
```

### 使用拉索算法

```python
from sklearn.linear_model import Lasso
reg = Lasso(alpha=0.1).fit(X, y)
```