2018年5月30日水曜日

開発環境

Pythonからはじめる数学入門 (Amit Saha (著)、黒川 利明 (翻訳)、オライリージャパン)の4章(SymPyで代数と式を計算する)、4.6(プログラミングチャレンジ)、問題4-2(グラフを使った方程式ソルバー)を取り組んでみる。

コード(Emacs)

Python 3

#!/usr/bin/env python3

from sympy import pprint, symbols, sympify, SympifyError, plot, solve

x, y = symbols('x, y')
if __name__ == '__main__':
    i = 0
    while True:
        expr1 = input('Enter your first expression in terms of x and y: ')
        if expr1 == 'q':
            break
        expr2 = input('Enter your second expression in terms of x and y: ')
        try:
            expr1 = sympify(expr1)
            expr2 = sympify(expr2)
        except SympifyError as err:
            print(type(err), err)
        else:
            s = solve((expr1, expr2), dict=True)
            for d in s:
                pprint(f'x = {d.get(x)}, y = {d.get(y)}')
            ys = solve(expr1, y) + solve(expr2, y)
            p = plot(*ys, legend=True, show=False)
            p.save(f'sample2_{i}.svg')
            i += 1

入出力結果(Terminal, Jupyter(IPython))

$ ./sample2.py
Enter your first expression in terms of x and y: y - x
Enter your second expression in terms of x and y: y - x - 1
Enter your first expression in terms of x and y: y - x
Enter your second expression in terms of x and y: y - 2 * x
x = 0, y = 0
Enter your first expression in terms of x and y: y - x ** 2 + 1
Enter your second expression in terms of x and y: y + x ** 2 - 2
x = -sqrt(6)/2, y = 1/2
x = sqrt(6)/2, y = 1/2
Enter your first expression in terms of x and y: y - x ** 2 - 1
Enter your second expression in terms of x and y: y + x ** 2 + 2
x = -sqrt(6)*I/2, y = -1/2
x = sqrt(6)*I/2, y = -1/2
Enter your first expression in terms of x and y: q
$



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