numpy_linspace.py

import numpy as np
import matplotlib.pyplot as plt

# linspace(start, stop)
x = np.linspace(0, 10)
# x → array([ 0.        ,  0.20408163,  0.40816327,  0.6122449 ,  0.81632653,
#         1.02040816,  1.2244898 ,  1.42857143,  1.63265306,  1.83673469,
#         2.04081633,  2.24489796,  2.44897959,  2.65306122,  2.85714286,
#         3.06122449,  3.26530612,  3.46938776,  3.67346939,  3.87755102,
#         4.08163265,  4.28571429,  4.48979592,  4.69387755,  4.89795918,
#         5.10204082,  5.30612245,  5.51020408,  5.71428571,  5.91836735,
#         6.12244898,  6.32653061,  6.53061224,  6.73469388,  6.93877551,
#         7.14285714,  7.34693878,  7.55102041,  7.75510204,  7.95918367,
#         8.16326531,  8.36734694,  8.57142857,  8.7755102 ,  8.97959184,
#         9.18367347,  9.3877551 ,  9.59183673,  9.79591837, 10.        ])
# x.size → 50

# 簡単なグラフ作成例
x = np.linspace(-2, 2)
y = x**2
plt.xlabel("x")
plt.ylabel("y")
plt.plot(x, y)
plt.show()


# linspace(start, stop, num)
x = np.linspace(0, 3.14, 5)
# x → array([0.   , 0.785, 1.57 , 2.355, 3.14 ])


# endpointの指定
x1 = np.linspace(0, 10, 5, endpoint=True)
# x → array([ 0. ,  2.5,  5. ,  7.5, 10. ])

x2 = np.linspace(0, 10, 5, endpoint=False)
# y → array([0., 2., 4., 6., 8.])

# pyplotで出力
plt.plot(x1, np.zeros_like(x), "o", label="endpoint=True")
plt.plot(x2, np.zeros_like(x)+0.5, "o", label="endpoint=False")
plt.ylim([-0.5, 1])
plt.show()


# retstepでstep取得
x, step = np.linspace(0, 3.14, 5, retstep=True)
# x → array([0.   , 0.785, 1.57 , 2.355, 3.14 ])
# step → 0.785

# startとstopを配列で指定
x = np.linspace([0,10], [5,20], 3, axis=0)
# x → array([[ 0. , 10. ],
#            [ 2.5, 15. ],
#            [ 5. , 20. ]])

x = np.linspace([0,10], [5,20], 3, axis=1)
# x → array([[ 0. ,  2.5,  5. ],
#            [10. , 15. , 20. ]])

# arangeとlinspaceの違い
x = np.arange(0, 100, 25)
# x → array([ 0, 10, 20, 30, 40, 50, 60, 70, 80, 90])

y = np.linspace(0, 100, 10)
# y → array([  0.        ,  11.11111111,  22.22222222,  33.33333333,
#             44.44444444,  55.55555556,  66.66666667,  77.77777778,
#             88.88888889, 100.        ])


# arangeとlinspaceの違い（最小限の引数）
x = np.arange(0, 50)
# x → array([ 0,  1,  2,  3,..., 49]) #1ずつ増える

y = np.linspace(0, 10)
# y → array([ 0.        ,  0.20408163,  0.40816327,..., 10.]) #50要素