def dnorm(mean, variance, size=1): if isinstance(size, int): size = size, return mean + np.sqrt(variance) * np.random.randn(*size) # For reproducibility np.random.seed(12345) N = 100 X = np.c_[dnorm(0, 0.4, size=N), dnorm(0, 0.6, size=N), dnorm(0, 0.2, size=N)] eps = dnorm(0, 0.1, size=N) beta = [0.1, 0.3, 0.5] y = np.dot(X, beta) + eps
时间: 2024-03-31 09:35:31 浏览: 69
这段代码是一个用于生成线性回归数据的 Python 函数。函数中包括:
- `dnorm` 函数:用于生成指定均值和方差的态分布数据。
- `N`:样本数量。
- `X`:自变量矩阵,其中包含三个列,分别代表三个自变量,每列的数据都是从不同的正态分布中生成的。
- `eps`:误差项,也是从正态分布中生成的。
- `beta`:系数向量,包含三个元素,分别代表三个自变量的系数。
- `y`:因变量向量,通过自变量矩阵和系数向量计算得到,同时加上了误差项。
在这个程序中,我们生成了一个多元线性回归模型,其中自变量包括三个变量,分别从不同的正态分布中生成,而因变量是通过自变量和系数向量的线性组合计算得到,同时加上了误差项。这个过程可以用于生成模拟数据,用于测试线性回归模型的拟合效果。
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def dnorm(mean, variance, size=1): if isinstance(size, int): size = size, return mean + np.sqrt(variance) * np.random.randn(*size)
这段代码定义了一个函数 `dnorm`,用于生成指定均值和方差的正态分布数据。具体来说,该函数接受三个参数:
- `mean`:均值。
- `variance`:方差。
- `size`:生成数据的数量或形状。
函数首先检查 `size` 是否为整数,如果是则将其转换为包含一个元素的元组,这是为了确保 `np.random.randn` 函数可以正确地生成指定形状的数据。然后,函数使用 `np.random.randn` 函数生成符合标准正态分布的随机数,将其乘以标准差并加上均值,以生成指定均值和方差的正态分布数据。最后,函数返回生成的数据。
这个函数可以用于生成模拟数据,用于测试统计模型的拟合效果。
def estimate_variance(xs: np.ndarray, ys: np.ndarray, affine: np.ndarray, translation: np.ndarray, responsibility: np.ndarray) -> float: """ Estimate the variance of GMM. For simplification, we assume all the Gaussian distributions share the same variance, and each feature dimension is independent, so the variance can be represented as a scalar. :param xs: a set of points with size (N, D), N is the number of samples, D is the dimension of points :param ys: a set of points with size (M, D), M is the number of samples, D is the dimension of points :param affine: an affine matrix with size (D, D) :param translation: a translation vector with size (1, D) :param responsibility: the responsibility matrix with size (N, M) :return: the variance of each Gaussian distribution, a float """ # TODO: change the code below and compute the variance of each Gaussian return 1
To compute the variance of each Gaussian distribution, we can use the following steps:
1. Transform the xs using the affine matrix and translation vector:
```
xs_transformed = xs.dot(affine) + translation
```
2. Compute the pairwise distance matrix between xs_transformed and ys:
```
distance_matrix = np.linalg.norm(xs_transformed[:, np.newaxis, :] - ys[np.newaxis, :, :], axis=2)
```
3. Compute the weighted sum of squared distances for each Gaussian:
```
weighted_distances = distance_matrix**2 * responsibility
sum_weighted_distances = np.sum(weighted_distances, axis=(0, 1))
```
4. Compute the total weight of all the points:
```
total_weight = np.sum(responsibility)
```
5. Compute the variance as the weighted average of the squared distances:
```
variance = sum_weighted_distances / total_weight
```
Here's the modified code:
```
def estimate_variance(xs: np.ndarray, ys: np.ndarray, affine: np.ndarray,
translation: np.ndarray, responsibility: np.ndarray) -> float:
"""
Estimate the variance of GMM.
For simplification, we assume all the Gaussian distributions share the same variance,
and each feature dimension is independent, so the variance can be represented as a scalar.
:param xs: a set of points with size (N, D), N is the number of samples, D is the dimension of points
:param ys: a set of points with size (M, D), M is the number of samples, D is the dimension of points
:param affine: an affine matrix with size (D, D)
:param translation: a translation vector with size (1, D)
:param responsibility: the responsibility matrix with size (N, M)
:return:
the variance of each Gaussian distribution, a float
"""
# Transform xs using the affine matrix and translation vector
xs_transformed = xs.dot(affine) + translation
# Compute the pairwise distance matrix between xs_transformed and ys
distance_matrix = np.linalg.norm(xs_transformed[:, np.newaxis, :] - ys[np.newaxis, :, :], axis=2)
# Compute the weighted sum of squared distances for each Gaussian
weighted_distances = distance_matrix**2 * responsibility
sum_weighted_distances = np.sum(weighted_distances, axis=(0, 1))
# Compute the total weight of all the points
total_weight = np.sum(responsibility)
# Compute the variance as the weighted average of the squared distances
variance = sum_weighted_distances / total_weight
return variance
```
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