http://www-tlab.math.ryukoku.ac.jp/wiki/index.php?PIP%2F2017%2Fhw1234
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# -*- coding: utf-8 -*- | |
from __future__ import division | |
from __future__ import print_function | |
import numpy as np | |
import os | |
def trueFunction(x): | |
return 0.2 * x + 0.5 | |
def gendat(n, seed = 0, nsig = 0.0): | |
np.random.seed(seed) | |
x = np.linspace(0.0, 10.0, num = n) | |
y = trueFunction(x) + nsig * np.random.randn(n) | |
return np.vstack((x, y)).T | |
if __name__ == '__main__': | |
N = 21 | |
login = os.getlogin() | |
try: | |
idnum = int(login[1:]) | |
except: | |
idnum = 0 | |
# N 個のデータを生成 | |
X = gendat(N, seed = idnum, nsig = 0.2) | |
# テキストファイルに保存 | |
np.savetxt('hoge.txt', X, fmt = '%.3f') | |
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# -*- coding: utf-8 -*- | |
from __future__ import division | |
from __future__ import print_function | |
import numpy as np | |
### 最小二乗法(正規方程式を解いてパラメータを求める) | |
# | |
# x と y は 同じ長さのベクトル | |
# | |
def solve(x, y): | |
N = len(x) # N: データ数 | |
X = np.vstack((np.ones(N), x)) # X: 2 x N 行列 | |
A = np.dot(X, X.T) # A = XX^T | |
b = np.dot(X, y) # b = XY^T | |
# 連立方程式 Aw = b の解 w を求める | |
w = np.linalg.solve(A, b) | |
return w | |
### 最小二乗法による直線あてはめを実行し,結果を表示 | |
# | |
# x と y は 同じ長さのベクトル | |
# | |
def estimate(x, y): | |
N = x.shape[0] | |
print('# N =', N) | |
print('# x =', x) | |
print('# y =', y) | |
w = solve(x, y) | |
print('# 推定されたパラメータ: ', w) | |
b, a = w # w[0] is b and w[1] is a | |
print('# 推定された直線の式: y =', a, '*x +', b) | |
if __name__ == '__main__': | |
### 講義資料 Q1 ### | |
x = np.array([0, 4, 8, 20]) | |
y = np.array([0, 1, -1, -2]) | |
estimate(x, y) | |
print() | |
### ファイルからデータを読み込み ### | |
fn = 'hoge.txt' | |
try: | |
data = np.loadtxt(fn) | |
except FileNotFoundError: | |
print(fn + ' is not found') | |
quit() | |
x = data[:, 0] # 1列目が x | |
y = data[:, 1] # 2列目が y | |
estimate(x, y) | |
print() | |
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