[英]Trying to understand an example script on ML
我正在尝试通过一个关于机器学习的示例脚本: 线性模型系数解释中的常见陷阱,但我无法理解某些步骤。 脚本的开头是这样的:
import numpy as np
import scipy as sp
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
from sklearn.datasets import fetch_openml
survey = fetch_openml(data_id=534, as_frame=True)
# We identify features `X` and targets `y`: the column WAGE is our
# target variable (i.e., the variable which we want to predict).
X = survey.data[survey.feature_names]
X.describe(include="all")
X.head()
# Our target for prediction is the wage.
y = survey.target.values.ravel()
survey.target.head()
from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
train_dataset = X_train.copy()
train_dataset.insert(0, "WAGE", y_train)
_ = sns.pairplot(train_dataset, kind='reg', diag_kind='kde')
我的问题出在线路上
y = survey.target.values.ravel()
survey.target.head()
如果我们在这些行之后立即检查survey.target.head()
,输出是
Out[36]:
0 5.10
1 4.95
2 6.67
3 4.00
4 7.50
Name: WAGE, dtype: float64
模型如何知道WAGE
是目标变量? 是不是必须显式声明?
行survey.target.values.ravel()
旨在展平数组,但在本例中它不是必需的。 survey.target 是一个 pd 系列(即 1 列数据框),survey.target.values 是一个 numpy 数组。 您可以将两者都用于训练/测试拆分,因为survey.target
只有 1 列。
type(survey.target)
pandas.core.series.Series
type(survey.target.values)
numpy.ndarray
如果我们只使用survey.target,您可以看到回归将起作用:
y = survey.target
X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
train_dataset = X_train.copy()
train_dataset.insert(0, "WAGE", y_train)
sns.pairplot(train_dataset, kind='reg', diag_kind='kde')
如果您有另一个数据集,例如 iris,我想将花瓣宽度与其余数据集进行回归。 您将使用方括号[]
调用 data.frame 的列:
from sklearn.datasets import load_iris
from sklearn.linear_model import LinearRegression
dat = load_iris(as_frame=True).frame
X = dat[['sepal length (cm)','sepal width (cm)','petal length (cm)']]
y = dat[['petal width (cm)']]
X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
LR = LinearRegression()
LR.fit(X_train,y_train)
plt.scatter(x=y_test,y=LR.predict(X_test))
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