Matrix Operation¶

Matrix Multiplication¶

In [97]:

ar = np.arange(10)
print (ar)
print (ar*2)

[0 1 2 3 4 5 6 7 8 9]
[ 0  2  4  6  8 10 12 14 16 18]

Matrix Summation and Substraction¶

In [98]:

ar = np.arange(10)
print (ar+2)
print (ar-2)

[ 2  3  4  5  6  7  8  9 10 11]
[-2 -1  0  1  2  3  4  5  6  7]

Trasnposing Matrix¶

In [99]:

ar = np.array([np.arange(10),np.arange(10)])
print ('ar :\n',ar)
print ('ar transposed :\n',ar.transpose())

ar :
 [[0 1 2 3 4 5 6 7 8 9]
 [0 1 2 3 4 5 6 7 8 9]]
ar transposed :
 [[0 0]
 [1 1]
 [2 2]
 [3 3]
 [4 4]
 [5 5]
 [6 6]
 [7 7]
 [8 8]
 [9 9]]

Selecting Elements base on criteria¶

np.where(array condition, value if true, value if false)

In [100]:

ar = np.array([(1,2,3,4,5),(11,12,13,14,15),(21,22,23,24,25)])
print ('Data : \n', ar)
np.where(ar%2==0,1,0) # select all even elements

Data : 
 [[ 1  2  3  4  5]
 [11 12 13 14 15]
 [21 22 23 24 25]]

Out[100]:

array([[0, 1, 0, 1, 0],
       [0, 1, 0, 1, 0],
       [0, 1, 0, 1, 0]])