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import matplotlib.pyplot as plt
import math
import numpy as np

# 微分方程式の関数
def dxdt(x, t):
    gradients = []
    for i in range(len(x)):
        gradients.append(1)
    return gradients

# オイラー法
def euler(num, x0, t0, tn, h):
    x = x0.copy()
    t = t0.copy()
    n = int((tn[0] - t0[0]) / h) #雑実装
    X = [[] for _ in range(num)]
    T = [[] for _ in range(num)]
    # 漸化式を計算
    for t_count in range(n):
        gradients = dxdt(x, t)
        for i in range(num):
            x[i] += gradients[i] * h
            X[i].append(x[i])
            t[i] = t0[i] + t_count * h
            T[i].append(t[i])
    return X, T

num = 4
X, T = euler(num, [0,1,2,5], [0 for _ in range(num)], [15 for _ in range(num)], 0.01)
print(X)
print(T)
for i in range(len(T)):
    plt.plot(T[i], X[i])
plt.show()