#範例5-6：矩陣的切割，切片（slice）
import numpy as np
#一維矩陣的切片，切割
a = np.arange(0,11)
print(a)

#切割(2:5:1) = 從index=2開始，到index=5-1=4, step=1
s1 = a[2:5:1]
print('切割(2:5:1)=',s1)

#切割(2:4) = 從index=2開始，到index=4-1=3
s1 = a[2:4]
print('切割(2:4)=',s1)

#切割(:4) = 從index=0開始，到index=4-1=3
s1 = a[:4]
print('切割(:4)=',s1)

#切割(2:9:2) = 從index=2開始，到index=9-1=8, step=2
s1 = a[2:9:2]
print('切割(2:9:2)=',s1)

#二維矩陣的切片，切割
a2 = np.arange(0,12).reshape(3,4)
print('reshape(3,4)=', a2)
#把a2切片 = a2[1:3,1:3]
s2 = a2[1:3,1:3]
print('a2[1:3,1:3]=',s2)


#把a2切片 = a2[:,::2] = [第一維全部顯示，第二維step2]
s2 = a2[:,::2]
print('a2[:,::2]=',s2)