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import numpy as np x=np.arange(10) x array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) X= np.arange(15).reshape(3,5) X array([[ 0, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[10, 11, 12, 13, 14]]) 基本屬性 x.ndim # 查看數組維數 1 X.ndim 2 x.shape (10,) X.shape (3, 5) x.size 10 X.size 15 numpy.array的數據訪問 x array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) x[0] 0 x[-1] 9 X array([[ 0, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[10, 11, 12, 13, 14]]) X[0][0] 0 X[(0,0)] 0 X[2,2] 12 x array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) x[0:5] array([0, 1, 2, 3, 4]) x[:5] array([0, 1, 2, 3, 4]) x[5:] array([5, 6, 7, 8, 9]) x[::2] #間隔 array([0, 2, 4, 6, 8]) x[::-1] #倒序 array([9, 8, 7, 6, 5, 4, 3, 2, 1, 0]) X array([[ 0, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[10, 11, 12, 13, 14]]) X[:2,:3] array([[0, 1, 2],[5, 6, 7]]) X[:2][:3] #前兩行的前三列 array([[0, 1, 2, 3, 4],[5, 6, 7, 8, 9]]) X[:2][:3] #X[:2]的前3行 array([[0, 1, 2, 3, 4],[5, 6, 7, 8, 9]]) X[:2,::2] array([[0, 2, 4],[5, 7, 9]]) X[::-1,::-1] array([[14, 13, 12, 11, 10],[ 9, 8, 7, 6, 5],[ 4, 3, 2, 1, 0]]) X[0] array([0, 1, 2, 3, 4]) X[0,:] array([0, 1, 2, 3, 4]) X[0,:].ndim 1 X[:,0] array([ 0, 5, 10]) X[:,0].ndim 1 subX=X[:2,:3] subX array([[0, 1, 2],[5, 6, 7]]) subX[0,0]=100 subX array([[100, 1, 2],[ 5, 6, 7]]) X #子矩陣對原矩陣右影響，子矩陣引用的原矩陣的元素 array([[100, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[ 10, 11, 12, 13, 14]]) X[0,0]=0 X array([[ 0, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[10, 11, 12, 13, 14]]) subX array([[0, 1, 2],[5, 6, 7]]) subX =X[:2,:3].copy() #副本 subX array([[0, 1, 2],[5, 6, 7]]) subX[0,0]=100 subX array([[100, 1, 2],[ 5, 6, 7]]) X array([[ 0, 1, 2, 3, 4],[ 5, 6, 7, 8, 9],[10, 11, 12, 13, 14]]) Reshape x.shape (10,) x.ndim 1 x.reshape(2,5) array([[0, 1, 2, 3, 4],[5, 6, 7, 8, 9]]) x array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) A= x.reshape(2,5) A array([[0, 1, 2, 3, 4],[5, 6, 7, 8, 9]]) x array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]) B= x.reshape(1,10) B #一維轉二維 array([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]) B.shape (1, 10) x.reshape(10,-1) #指定行數，智能計算列數 array([[0],[1],[2],[3],[4],[5],[6],[7],[8],[9]]) x.reshape(-1,10) array([[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]) x.reshape(2,-1) array([[0, 1, 2, 3, 4],[5, 6, 7, 8, 9]]) x.reshape(3,-1) --------------------------------------------------------------------------- ValueError Traceback (most recent call last) <ipython-input-65-27fb2acd3ab6> in <module> ----> 1 x.reshape(3,-1)ValueError: cannot reshape array of size 10 into shape (3,newaxis)

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