Python-Numpy(3)矩阵基本操作

import numpy as np
a = np.arange(15).reshape(3, 5)
a

a.shape

#the number of axes (dimensions) of the array
a.ndim#维度

a.dtype.name

#the total number of elements of the array
a.size

np.zeros ((3,4)) 

np.ones( (2,3,4), dtype=np.int32 )

#To create sequences of numbers
np.arange( 10, 30, 5 )

np.arange( 0, 2, 0.3 )

np.arange(12).reshape(4,3)

np.random.random((2,3))

from numpy import pi
np.linspace( 0, 2*pi, 100 )

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

#the product operator * operates elementwise in NumPy arrays
a = np.array( [20,30,40,50] )
b = np.arange( 4 )
#print a 
#print b
#b
c = a-b
#print c
b**2
#print b**2
print a<35

#The matrix product can be performed using the dot function or method
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)