NumPy詳細API第三篇

注意：以下代碼是基於python3.5.0編寫的

import numpy as np
a = np.arange(15).reshape(3, 5)
print(a)        #  array([[ 0,  1,  2,  3,  4],[ 5,  6,  7,  8,  9],[10, 11, 12, 13, 14]])
print(a.shape)              # (3, 5)
print(a.ndim)               # 2
print(a.dtype.name)         # 'int32'
print(a.size)               # 15

# -----------------全零矩陣-----------------
np.zeros ((3,4)）    # array([[ 0.,  0.,  0.,  0.], [ 0.,  0.,  0.,  0.], [ 0.,  0.,  0.,  0.]])

# -----------------全1矩陣-----------------
np.ones( (2,3,4), dtype=np.int32 )
# array([[[1, 1, 1, 1],[1, 1, 1, 1],[1, 1, 1, 1]],
#          [[1, 1, 1, 1],[1, 1, 1, 1],[1, 1, 1, 1]]])

# ---------------指定矩陣起始值爲10，終止值爲30但不包含30，間隔爲5--------------
np.arange( 10, 30, 5 )          #array([10, 15, 20, 25])

# ----------------初始化的2行3列，值在0到1之間-----------------
np.random.random((2,3))

# ----------------0到2*pi之間生成100個值，且每個值間隔相等---------------------
from numpy import pi
np.linspace( 0, 2*pi, 100 )

# --------------------sin函數----------------------
np.sin(np.linspace( 0, 2*pi, 100 ))

# ----------------------矩陣的常規算數運算-----------------------
a = np.array( [20,30,40,50] )
b = np.arange( 4 )
c = a-b
d=b**2
print(a<35)              # 返回布爾值[ True  True False False]

# ----------------------------矩陣乘法--------------------------
A = np.array( [[1,1],
               [0,1]] )
B = np.array( [[2,0],
               [3,4]] )
print(A)
print(B)
#print A*B
print(A.dot(B))
print(np.dot(A, B))