Numpy 2

 

>>> import numpy a
>>> list = [
... [1,2,3],
... [4,5,6],
... [7,8,9]
... ]
>>> arr = np.array
>>> arr
array([[1, 2, 3],
       [4, 5, 6],
       [7, 8, 9]])
>>> 

>>> a = arr[0:2, 0
>>> a
array([[1, 2],
       [4, 5]])
>>> 
>>> b=arr[1:, 1:]
>>> b
array([[5, 6],
       [8, 9]])

numpy 정수 인덱싱 (integer indexing)

# 정수 인덱싱 : numpy 배열 a에 대해서 a[[row1, row2] , [col1, col2]] = a[row1,col1]과 a[row2,col2] 배열 요소 집합

>>> list = [
... [1,2,3,4],
... [5,6,7,8],
... [9,10,11,12]
... ]
>>> a = np.array(list)
>>> 
>>> #정수 인덱싱
>>> res = a[[0,2], [1,3]]
>>> res
array([ 2, 12])

 

# 부울린 인덱싱 

>>> list1 = [
... [1,2,3],
... [4,5,6],
... [7,8,9]
... ]
>>> 
>>> aa = np.array(list1)
>>> b_arr = np.array([
... [False, True, False],
... [True, False, True],
... [False, True, False]
... ])
>>> 
>>> b_arr
array([[False,  True, False],
       [ True, False,  True],
       [False,  True, False]])
>>> n = aa[b_arr]
>>> 
>>> n
array([2, 4, 6, 8])

 

# 부울린