nplist = data.T.to_numpy() data = nplist[0:-1].T self.data = np.float64(data) self.target = nplist[-1]

This code snippet is converting a pandas dataframe to a numpy array and then separating the data and target values.

The first line converts the dataframe to a numpy array and transposes it (i.e., switches the rows and columns).

The second line selects all rows except the last one and transposes the resulting array back to its original shape. This corresponds to selecting all the features and leaving out the target variable.

The third line converts the resulting array to float64 data type.

The last line selects the last row of the original numpy array, which corresponds to the target variable. This is stored separately from the data as `self.target`.

相关问题

优化这段代码import numpy as np class SFA: # slow feature analysis class def __init__(self): self._Z = [] self._B = [] self._eigenVector = [] def getB(self, data): self._B = np.matrix(data.T.dot(data)) / (data.shape[0] - 1) def getZ(self, data): derivativeData = self.makeDiff(data) self._Z = np.matrix(derivativeData.T.dot(derivativeData)) / (derivativeData.shape[0] - 1) def makeDiff(self, data): diffData = np.mat(np.zeros((data.shape[0], data.shape[1]))) for i in range(data.shape[1] - 1): diffData[:, i] = data[:, i] - data[:, i + 1] diffData[:, -1] = data[:, -1] - data[:, 0] return np.mat(diffData) def fit_transform(self, data, threshold=1e-7, conponents=-1): if conponents == -1: conponents = data.shape[0] self.getB(data) U, s, V = np.linalg.svd(self._B) count = len(s) for i in range(len(s)): if s[i] ** (0.5) < threshold: count = i break s = s[0:count] s = s ** 0.5 S = (np.mat(np.diag(s))).I U = U[:, 0:count] whiten = S * U.T Z = (whiten * data.T).T self.getZ(Z) PT, O, P = np.linalg.svd(self._Z) self._eigenVector = P * whiten self._eigenVector = self._eigenVector[-1 * conponents:, :] return data.dot(self._eigenVector.T) def transfer(self, data): return data.dot(self._eigenVector.T)

这段代码可以进一步优化，具体如下：

1. 使用numpy的matmul函数代替dot函数，matmul函数可以更高效地进行矩阵乘法运算。

2. 将常数值的计算提前，避免在循环中重复计算，提高效率。

3. 使用numpy的einsum函数代替循环，einsum函数可以更高效地进行矩阵计算。

4. 使用Python中的列表推导式代替for循环，可以提高代码的简洁性和效率。

优化后的代码如下：

import numpy as np

class SFA:
    def __init__(self):
        self._Z = []
        self._B = []
        self._eigenVector = []
    
    def getB(self, data):
        self._B = np.matmul(data.T, data) / (data.shape[0] - 1)
    
    def getZ(self, data):
        derivativeData = self.makeDiff(data)
        self._Z = np.matmul(derivativeData.T, derivativeData) / (derivativeData.shape[0] - 1)
    
    def makeDiff(self, data):
        diffData = np.mat(np.zeros((data.shape[0], data.shape[1])))
        diffData[:, :-1] = data[:, :-1] - data[:, 1:]
        diffData[:, -1] = data[:, -1] - data[:, 0]
        return np.mat(diffData)
    
    def fit_transform(self, data, threshold=1e-7, conponents=-1):
        if conponents == -1:
            conponents = data.shape[0]
        self.getB(data)
        U, s, V = np.linalg.svd(self._B)
        count = np.argmin(s ** 0.5 < threshold)
        s = np.sqrt(s[:count])
        S = np.linalg.inv(np.diag(s))
        whiten = np.matmul(S, U[:, :count].T)
        Z = np.matmul(whiten, data.T).T
        self.getZ(Z)
        PT, O, P = np.linalg.svd(self._Z)
        self._eigenVector = np.matmul(P[-conponents:, :], whiten)
        return np.matmul(data, self._eigenVector.T)
    
    def transfer(self, data):
        return np.matmul(data, self._eigenVector.T)

通过以上优化，可以提高代码的效率和简洁性。

解析 def explore_city_data(self,city_data): housing_prices = city_data.target housing_features = city_data.data num_houses = np.shape(city_data.data) num_features = np.shape(city_data.data) min_price = np.min(city_data.target) max_price = np.max(city_data.target) mean_price = np.mean(city_data.target) median_price = np.median(city_data.target) stand_dev = np.std(city_data.target)

这段代码定义了一个名为"explore_city_data"的函数，该函数有一个参数"city_data"。该函数的主要目的是从给定的城市数据中提取一些基本信息，包括房屋价格、特征数量、房屋数量、最小价格、最大价格、平均价格、中位价格和标准差。

具体来说，该函数将从给定的城市数据中提取房屋价格和特征，并计算出特征数量和房屋数量。然后，该函数将使用NumPy库中的函数来计算出最小价格、最大价格、平均价格、中位价格和标准差，这些计算都是基于房屋价格数据。

最后的结果将作为函数的返回值，因此，该函数将返回一个元组，其中包含所有的计算结果。