陣列重塑  2018/11/25
    
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1.a.reshape(shape, order='C')
    # 無需複製資料，陣列就能從一個形狀轉換為另一個形狀
    # shape其中一維可以是-1 ，該維度的大小由資料本身推斷而來
    
a=np.arange(6,dtype=int).reshape(2,3)   #array([[0, 1, 2],[3, 4, 5]])
np.reshape(np.arange(6,dtype=int),(2,3))#array([[0, 1, 2], [3, 4, 5]])
    
np.reshape(a, (3,-1))    # -1預設值自動被指定為2:shape=3*2  # array([[1, 2],[3, 4],[5, 6]])
np.reshape(a, (2,-1))    # -1預設值自動被指定為3:shape=2*3  # array([[1, 2, 3],[4, 5, 6]])
    
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2.resize修改原陣列形狀
    
np.resize（a，new_shape）拷貝的副本，原陣列不改變
    #返回具有指定形狀的新陣列。重複的a副本，必要時指定數量。無refcheck引數
a.resize（new_shape，refcheck = True）就地操作，改變原陣列
    #新陣列用a填充，不足的填充0，不同與上面函式。
    # refcheck=True檢查引用計數，預設禁止陣列放大或縮小；False可放大縮小
    # 只有連續的陣列（記憶體中連續的資料元素）可以調整大小
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a = np.array([[0, 1], [2, 3]], order='C')# array([[0, 1], [2, 3]])
a.resize((4,1))                                    # array([[0], [1], [2],[3]])
    
a = np.array([[0, 1], [2, 3]], order='C')
# a.resize((2, 1))                                # 錯誤-收縮陣列                    # array([[0],[1]])
a.resize((2, 1),refcheck = False)       # 收縮陣列被平展（儲存記憶體中順序）調整大小和重新定形
    
a = np.array([[0, 1], [2, 3]], order='C')
# a.resize(2, 3)                                  # 錯誤-放大陣列
a.resize((2, 3),refcheck = False)       # 放大陣列：缺少填充零      # array([[0, 1, 2],[3, 0, 0]])
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a = np.array([[0, 1], [2, 3]], order='C')
np.resize(a,(4,1))                                                     # array([[0], [1], [2],[3]])

a = np.array([[0, 1], [2, 3]], order='C')
np.resize(a,(2, 1))                                # 收縮陣列   # array([[0],[1]])

a = np.array([[0, 1], [2, 3]], order='C')
np.resize(a,(3, 3))                                # 放大陣列   # array([[0, 1, 2], [3, 0, 1], [2, 3, 0]])
    
a                                                                              # array([[0, 1],[2, 3]])
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3.轉置np.transpose(a, axes=None)#是重塑一種特殊形式，返回據資料的檢視

無引數：反轉軸的順序；對於a.shape=(2, 3)的陣列必須是無引數
(i,j)引數類似軸i,j互換
    
例項1：# 對於一維陣列，這不起作用；
a=np.arange(6).reshape(2,3)# array([[0, 1, 2],[3, 4, 5]])
    
a.T                     # array([[0, 3], [1, 4], [2, 5]])
a.transpose()     # array([[0, 3],[1, 4],[2, 5]])
# a.transpose(0)# 錯誤
# a.transpose(1)# 錯誤
    

例項2：#對於高維陣列， transpose需要一組軸編號：
    
a
array([[[ 0,  1,  2],
            [ 3,  4,  5]],
           [[ 6,  7,  8],
            [ 9, 10, 11]]])
    
a.transpose(0,1,2)# a0.shape# (2, 2, 3) 原形狀(2, 2, 3)
array([[[ 0,  1,  2],
            [ 3,  4,  5]],
           [[ 6,  7,  8],
            [ 9, 10, 11]]])
    
a.transpose(1,0,2)# a1.shape# (2, 2, 3)原形狀(2, 2, 3)
array([[[ 0,  1,  2],
            [ 6,  7,  8]],
           [[ 3,  4,  5],
            [ 9, 10, 11]]])
    
a.transpose(0,2,1)# a2.shape# (2, 3, 2)原形狀(2, 2, 3)
    
array([[[ 0,  3],
            [ 1,  4],
            [ 2,  5]],
           [[ 6,  9],
            [ 7, 10],
            [ 8, 11]]])
    
a.transpose(2,0,1)# a3.shape#(3, 2, 2)原形狀(2, 2, 3)
array([[[ 0,  3],
            [ 6,  9]],
           [[ 1,  4],
            [ 7, 10]],
           [[ 2,  5],
            [ 8, 11]]])
    
a.transpose(1,2,0)# a4.shape#(2, 3, 2)原形狀(2, 2, 3)
array([[[ 0,  6],
            [ 1,  7],
            [ 2,  8]],
           [[ 3,  9],
            [ 4, 10],
            [ 5, 11]]])
    
a.transpose(2,1,0)# a5.shape#(3, 2, 2)原形狀(2, 2, 3)
array([[[ 0,  6],
            [ 3,  9]],
           [[ 1,  7],
            [ 4, 10]],
           [[ 2,  8],
            [ 5, 11]]])
a.T                                         # array([[[ 0,  6], [ 3,  9]],[[ 1,  7],[ 4, 10]], [[ 2,  8],[ 5, 11]]])

    
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 備註：transpose的實現原理
    
基本原理：相同位置不變換，其他位置對換以3維陣列為例。
本程式模擬實現轉置，其他4條能夠模擬實現，2條有問題歡迎大家修正。
import numpy as np
        
a=np.arange(12).reshape(2,2,3)
def testview(a0=a):
    for i in range(a0.shape[0]):
        for m in range(a0.shape[1]):
            for n in range(a0.shape[2]):
                print('ss=',a0[i, m, n], end=",")
            print('ss=','')
        
def computer_i_m_n(zi0=0,zm0=1,zn0=2,a0=a):
    i, m, n = a0.shape
    i1, m1, n1 = 0, 0, 0
    if zi0 == 0:
        if zm0 == 1:
            i1, m1, n1 = i, m, n
        else:
            i1, m1, n1 = i, n, m
    elif zi0 == 1:
        if zm0 == 0:
            i1, m1, n1 = m, i, n
        else:
            i1, m1, n1 = m, n, i
    elif zi0 == 2:
        if zm0 == 0:
            i1, m1, n1 = n, i, m
        else:
            i1, m1, n1 = n, m, i
    return i1,m1,n1
    
def swap_old_new_arr(i1,m1,n1,zi0=0,zm0=1,zn0=2):

    if zi0 == 0:
        if zm0 == 1:
             return i1, m1, n1
        else:
             return  i1, n1, m1
    elif zi0 == 1:
        if zm0 == 0:
             return m1, i1, n1
        else:
             return m1, n1, i1
    elif zi0 == 2:
        if zm0 == 0:
             return n1, i1, m1#3,2,2
        else:
             return n1, m1, i1

    
def test(zi0=0,zm0=1,zn0=2,a0=a):

    i1,m1,n1=computer_i_m_n(zi0=zi0,zm0=zm0,zn0=zn0,a0=a0)
    i3,m3,n3=0,0,0
    new_a=np.arange(i1*m1*n1).reshape(i1,m1,n1)
    # i2,m2,n2=0,0,0
    for i2 in range(i1):
         for m2 in range(m1):
             for n2 in range(n1):
                i3,m3,n3=swap_old_new_arr(i1=i2, m1=m2, n1=n2, zi0=zi0, zm0=zm0, zn0=zn0)
                new_a[i2,m2,n2]=a0[i3,m3,n3]
    
    return new_a
    
print('ss=',test(0,1,2))
print('ss=',test(0,2,1))
print('ss=',test(1,0,2))
# print('ss=',test(1,2,0))問題？？報錯，請高手修改
# print('ss=',test(2,0,1))問題？？報錯，請高手修改
print('ss=',test(2,1,0))