[data science] Numpy

*jupyter notebook에서 작성

import numpy as np

input>>
array1 = np.array([1,3,5,6,7,9])
array1
output>>
array([1, 3, 5, 6, 7, 9])

input>>
np.zeros(5)
output>>
array([0., 0., 0., 0., 0.])

input>>
np.arange(10)
output>>
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

input>>
np.arange(2 , 10)
output>>
array([2, 3, 4, 5, 6, 7, 8, 9])

input>>
np.arange(4,17,3)
output>>
array([ 4,  7, 10, 13, 16])

input>>
type(array1)
output>>
numpy.ndarray

input>>
aarray2 = np.array([[1,2,3,4],[5,6,7,8],[9,10,11,12]])
array2
output>>
array([[ 1,  2,  3,  4],
       [ 5,  6,  7,  8],
       [ 9, 10, 11, 12]])
    
input>>
array2.size
output>>
12

input>>
array2.shape
output>>
(3, 4)

input>>
gdp_array = np.array([6610,7637,8127,8885,10385,13403,12398,8282,10672])
output>>
gdp_array[0]
6610
gdp_array[-1]
10672

input>>
gdp_array[[1, 3, 4]]
output>>
array([ 7637,  8885, 10385])

input>>
array1= np.array([2,1,3,5])
gdp_array[array1]
output>>
array([ 8127,  7637,  8885, 13403])

input>>
gdp_array[2:6]
output>>
array([ 8127,  8885, 10385, 13403])

gdp_array[1:8:3]

array([ 7637, 10385,  8282])

예제

import numpy as np

bitcoin_array = np.array([970, 1180, 1072, 1348, 2286, 2481,
                          2875, 4703, 4339, 6468, 10234, 14156])

bitcoin_array[6:9]
</> 실행 결과
array([2875, 4703, 4339])



gdp_array = np.array([
    [12257, 11561, 13165, 14673, 16496, 19403],  # 대한민국
    [39169, 34406, 32821, 35387, 38299, 37813],  # 일본
    [959, 1053, 1149, 1289, 1509, 1753],         # 중국
    [36335, 37133, 38023, 39496, 41713, 44115]   # 미국
])
gdp_array

array([[12257, 11561, 13165, 14673, 16496, 19403],
       [39169, 34406, 32821, 35387, 38299, 37813],
       [  959,  1053,  1149,  1289,  1509,  1753],
       [36335, 37133, 38023, 39496, 41713, 44115]])
       
gdp_array[1]       
 array([39169, 34406, 32821, 35387, 38299, 37813])      
 
gdp_array[1:3 , 2:5]
array([[32821, 35387, 38299],
       [ 1149,  1289,  1509]])
       
gdp_array[: , 2:5]   

array([[13165, 14673, 16496],
       [32821, 35387, 38299],
       [ 1149,  1289,  1509],
       [38023, 39496, 41713]])