[英]Linear regression prediction not matching training data
I am a newbie to machine learning.我是机器学习的新手。 I am trying a simple prediction using linear regression with "made up" data that follows a specific pattern.
我正在尝试使用线性回归和遵循特定模式的“合成”数据进行简单预测。 For some reason, the prediction is not matching the training data.
由于某种原因,预测与训练数据不匹配。 Can you let me know what I need to fix?
你能告诉我我需要修复什么吗? The sample code is below
示例代码如下
from sklearn import linear_model
import numpy as np
X = np.random.randint(3, size=(3, 1000))
Y = np.random.randint(10, size=(1, 1000))
# f1, f2, f3 - min = 0, max = 2
# f1 = 0 and f2 = 1 then 7 <= Y < 10, irrespective of f3
# f1 = 1 and f2 = 2 Y is 0, irrespective of f3
# f1 = 0 and f2 = 2 if f3 = 2 then 3 <= Y < 7 else Y = 0
for i in range(1000):
if ((X[0][i] == 0 and X[1][i] == 1) or (X[0][i] == 1 and X[1][i] == 0)):
Y[0][i] = np.random.randint(7, 10)
elif ((X[0][i] == 1 and X[1][i] == 2) or (X[0][i] == 2 and X[1][i] == 1)):
Y[0][i] = 0
elif ((X[0][i] == 0 and X[1][i] == 2 and X[2][i] == 2) or
(X[0][i] == 2 and X[1][i] == 0 and X[2][i] == 2)):
Y[0][i] = np.random.randint(3, 7)
else:
Y[0][i] = 0
X1 = X.transpose()
Y1 = Y.reshape(-1, 1)
print zip(X1, Y1)
# create and fit the model
clf = linear_model.LinearRegression()
clf.fit(X1, Y1)
Z = np.array([[0, 0, 0, 0, 1, 1],
[1, 1, 2, 2, 2, 2],
[1, 2, 1, 2, 1, 2]])
Z1 = Z.transpose()
print Z1
y_predict = clf.predict(Z1)
print y_predict
And why would it match the training data?为什么它会匹配训练数据? Your X->Y relation is clearly non-linear, and only for perfect linear relation, meaning that Y = AX + b, you can expect linear regression to fit training data perfectly.
您的 X->Y 关系显然是非线性的,并且仅适用于完美的线性关系,这意味着 Y = AX + b,您可以期望线性回归完美地拟合训练数据。 Otherwise, you can get arbitrary far away from the solution - see for example an Anscombe's quartet (image belowo from wiki).
否则,您可以随意远离解决方案 - 例如,请参见 Anscombe 的四重奏(来自 wiki 的下图)。
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